diff --git a/apis/api-gateway/schema.graphql b/apis/api-gateway/schema.graphql
index 8f4e6cd71e3..585128dd8ef 100644
--- a/apis/api-gateway/schema.graphql
+++ b/apis/api-gateway/schema.graphql
@@ -550,6 +550,7 @@ type Mutation @join__type(graph: API_ANALYTICS)  @join__type(graph: API_JOURNEYS
   videoEditionCreate(input: VideoEditionCreateInput!) : VideoEdition! @join__field(graph: API_MEDIA) 
   videoEditionUpdate(input: VideoEditionUpdateInput!) : VideoEdition! @join__field(graph: API_MEDIA) 
   videoEditionDelete(id: ID!) : VideoEdition! @join__field(graph: API_MEDIA) 
+  mergeGuest(input: MergeGuestInput!) : User! @join__field(graph: API_USERS) 
   userImpersonate(email: String!) : String @join__field(graph: API_USERS) 
   createVerificationRequest(input: CreateVerificationRequestInput) : Boolean @join__field(graph: API_USERS) 
   validateEmail(email: String!, token: String!) : User @join__field(graph: API_USERS) 
@@ -2185,9 +2186,10 @@ type User @join__type(graph: API_JOURNEYS, key: "id", extension: true)  @join__t
   id: ID!
   languageUserRoles: [LanguageRole!]! @join__field(graph: API_LANGUAGES) 
   mediaUserRoles: [MediaRole!]! @join__field(graph: API_MEDIA) 
+  userId: String! @join__field(graph: API_USERS) 
   firstName: String! @join__field(graph: API_USERS) 
   lastName: String @join__field(graph: API_USERS) 
-  email: String! @join__field(graph: API_USERS) 
+  email: String @join__field(graph: API_USERS) 
   imageUrl: String @join__field(graph: API_USERS) 
   superAdmin: Boolean @join__field(graph: API_USERS) 
   emailVerified: Boolean! @join__field(graph: API_USERS) 
@@ -5454,5 +5456,12 @@ input CreateVerificationRequestInput @join__type(graph: API_USERS)  {
 
 input MeInput @join__type(graph: API_USERS)  {
   redirect: String
+  createGuestIfAnonymous: Boolean
+}
+
+input MergeGuestInput @join__type(graph: API_USERS)  {
+  firstName: String!
+  lastName: String!
+  email: String!
 }
     
\ No newline at end of file
diff --git a/apis/api-journeys/src/app/modules/mailChimp/mailChimp.service.spec.ts b/apis/api-journeys/src/app/modules/mailChimp/mailChimp.service.spec.ts
index 90079280a26..a9c054733a2 100644
--- a/apis/api-journeys/src/app/modules/mailChimp/mailChimp.service.spec.ts
+++ b/apis/api-journeys/src/app/modules/mailChimp/mailChimp.service.spec.ts
@@ -92,5 +92,16 @@ describe('MailChimpService', () => {
         'Mailchimp Audience ID is undefined'
       )
     })
+
+    it('should no-op when user has no email (e.g. anonymous/guest)', async () => {
+      const userWithoutEmail: User = {
+        ...user,
+        email: null
+      }
+      await expect(
+        mailChimpService.syncUser(userWithoutEmail)
+      ).resolves.toBeUndefined()
+      expect(mailchimp.lists.setListMember).not.toHaveBeenCalled()
+    })
   })
 })
diff --git a/apis/api-journeys/src/app/modules/mailChimp/mailChimp.service.ts b/apis/api-journeys/src/app/modules/mailChimp/mailChimp.service.ts
index 047037ef187..18ab143065a 100644
--- a/apis/api-journeys/src/app/modules/mailChimp/mailChimp.service.ts
+++ b/apis/api-journeys/src/app/modules/mailChimp/mailChimp.service.ts
@@ -8,14 +8,13 @@ import { User } from '../../lib/firebaseClient'
 export class MailChimpService {
   async syncUser(user: User): Promise<void> {
     try {
+      if (user.email == null) return
       mailchimp.setConfig({
         apiKey: process.env.MAILCHIMP_MARKETING_API_KEY,
         server: process.env.MAILCHIMP_MARKETING_API_SERVER_PREFIX
       })
       if (process.env.MAILCHIMP_AUDIENCE_ID == null)
         throw new Error('Mailchimp Audience ID is undefined')
-      if (user.email == null)
-        throw new Error('User must have an email to receive marketing emails')
       // upsert operation
       await mailchimp.lists.setListMember(
         process.env.MAILCHIMP_AUDIENCE_ID,
diff --git a/apis/api-users/schema.graphql b/apis/api-users/schema.graphql
index e8efcd93300..42358945e37 100644
--- a/apis/api-users/schema.graphql
+++ b/apis/api-users/schema.graphql
@@ -7,9 +7,17 @@ input CreateVerificationRequestInput {
 
 input MeInput {
   redirect: String
+  createGuestIfAnonymous: Boolean
+}
+
+input MergeGuestInput {
+  firstName: String!
+  lastName: String!
+  email: String!
 }
 
 type Mutation {
+  mergeGuest(input: MergeGuestInput!): User!
   userImpersonate(email: String!): String
   createVerificationRequest(input: CreateVerificationRequestInput): Boolean
   validateEmail(email: String!, token: String!): User
@@ -25,9 +33,10 @@ type User
   @key(fields: "id")
 {
   id: ID!
+  userId: String!
   firstName: String!
   lastName: String
-  email: String!
+  email: String
   imageUrl: String
   superAdmin: Boolean
   emailVerified: Boolean!
diff --git a/apis/api-users/src/schema/user/findOrFetchUser.spec.ts b/apis/api-users/src/schema/user/findOrFetchUser.spec.ts
index 578ac30459e..07af84fc05f 100644
--- a/apis/api-users/src/schema/user/findOrFetchUser.spec.ts
+++ b/apis/api-users/src/schema/user/findOrFetchUser.spec.ts
@@ -6,14 +6,15 @@ import { verifyUser } from './verifyUser'
 
 jest.mock('@core/yoga/firebaseClient', () => ({
   auth: {
-    getUser: jest.fn().mockReturnValue({
+    getUser: jest.fn().mockResolvedValue({
       id: '1',
       userId: '1',
       createdAt: new Date('2021-01-01T00:00:00.000Z'),
       displayName: 'Amin One',
       email: 'amin@email.com',
       photoURL: 'https://bit.ly/3Gth4',
-      emailVerified: false
+      emailVerified: false,
+      providerData: [{ providerId: 'google.com' }]
     })
   }
 }))
@@ -41,7 +42,7 @@ describe('findOrFetchUser', () => {
     const data = await findOrFetchUser({}, 'userId', undefined)
     expect(data).toEqual(user)
     expect(prismaMock.user.update).toHaveBeenCalledWith({
-      where: { id: 'userId' },
+      where: { userId: 'userId' },
       data: { emailVerified: false }
     })
   })
@@ -67,4 +68,71 @@ describe('findOrFetchUser', () => {
       undefined
     )
   })
+
+  it('should return null and not create database user for anonymous Firebase user', async () => {
+    const { auth } = await import('@core/yoga/firebaseClient')
+    ;(auth.getUser as jest.Mock).mockResolvedValueOnce({
+      id: 'anon',
+      userId: 'anonymousUserId',
+      displayName: null,
+      email: null,
+      photoURL: null,
+      emailVerified: false,
+      providerData: []
+    })
+    prismaMock.user.findUnique.mockResolvedValueOnce(null)
+    const data = await findOrFetchUser({}, 'anonymousUserId', undefined)
+    expect(data).toBeNull()
+    expect(prismaMock.user.create).not.toHaveBeenCalled()
+  })
+
+  it('should return existing user when create fails (e.g. concurrent create)', async () => {
+    prismaMock.user.findUnique
+      .mockResolvedValueOnce(null)
+      .mockResolvedValueOnce(user)
+    prismaMock.user.create.mockRejectedValueOnce(new Error('Unique constraint'))
+    const data = await findOrFetchUser({}, 'userId', undefined)
+    expect(data).toEqual(user)
+    expect(prismaMock.user.create).toHaveBeenCalledTimes(1)
+    expect(prismaMock.user.findUnique).toHaveBeenCalledTimes(2)
+  })
+
+  it('should create database user for anonymous Firebase user when forceCreateForAnonymous is true', async () => {
+    const { auth } = await import('@core/yoga/firebaseClient')
+    ;(auth.getUser as jest.Mock).mockResolvedValueOnce({
+      id: 'anon',
+      userId: 'anonymousUserId',
+      displayName: null,
+      email: null,
+      photoURL: null,
+      emailVerified: false,
+      providerData: []
+    })
+    const createdUser = {
+      ...user,
+      userId: 'anonymousUserId',
+      firstName: 'Unknown User',
+      lastName: '',
+      email: null,
+      emailVerified: false
+    }
+    prismaMock.user.findUnique.mockResolvedValueOnce(null)
+    prismaMock.user.create.mockResolvedValueOnce(
+      createdUser as unknown as typeof user
+    )
+    const data = await findOrFetchUser({}, 'anonymousUserId', undefined, {
+      forceCreateForAnonymous: true
+    })
+    expect(data).toEqual(createdUser)
+    expect(prismaMock.user.create).toHaveBeenCalledWith({
+      data: {
+        userId: 'anonymousUserId',
+        firstName: 'Unknown User',
+        lastName: '',
+        email: null,
+        imageUrl: null,
+        emailVerified: false
+      }
+    })
+  })
 })
diff --git a/apis/api-users/src/schema/user/findOrFetchUser.ts b/apis/api-users/src/schema/user/findOrFetchUser.ts
index 4547c686b55..f900cd24d2f 100644
--- a/apis/api-users/src/schema/user/findOrFetchUser.ts
+++ b/apis/api-users/src/schema/user/findOrFetchUser.ts
@@ -3,11 +3,19 @@ import { auth } from '@core/yoga/firebaseClient'
 
 import { verifyUser } from './verifyUser'
 
+export type FindOrFetchUserOptions = {
+  /** When true, create a database user even for anonymous Firebase users (e.g. "Create Guest"). */
+  forceCreateForAnonymous?: boolean
+}
+
 export async function findOrFetchUser(
   query: { select?: Prisma.UserSelect; include?: undefined },
   userId: string,
-  redirect: string | undefined = undefined
+  redirect: string | undefined = undefined,
+  options: FindOrFetchUserOptions = {}
 ): Promise<User | null> {
+  const { forceCreateForAnonymous = false } = options
+
   const existingUser = await prisma.user.findUnique({
     ...query,
     where: {
@@ -17,7 +25,7 @@ export async function findOrFetchUser(
   if (existingUser != null && existingUser.emailVerified == null) {
     const user = await prisma.user.update({
       where: {
-        id: userId
+        userId
       },
       data: {
         emailVerified: false
@@ -29,12 +37,17 @@ export async function findOrFetchUser(
   if (existingUser != null && existingUser.emailVerified != null)
     return existingUser
 
-  const {
-    displayName,
-    email,
-    emailVerified,
-    photoURL: imageUrl
-  } = await auth.getUser(userId)
+  const firebaseUser = await auth.getUser(userId)
+
+  const isAnonymous =
+    firebaseUser.providerData == null || firebaseUser.providerData.length === 0
+
+  // Do not create a database user for anonymous Firebase users unless explicitly requested.
+  if (isAnonymous && !forceCreateForAnonymous) {
+    return null
+  }
+
+  const { displayName, email, emailVerified, photoURL: imageUrl } = firebaseUser
 
   // Extract firstName and lastName from displayName with better fallbacks
   let firstName = ''
@@ -60,36 +73,31 @@ export async function findOrFetchUser(
     firstName = 'Unknown User'
   }
 
-  const data = {
+  // Schema has email String?; use assertion so nullable email compiles with any Prisma client version
+  const createData = {
     userId,
     firstName,
     lastName,
-    email: email ?? '',
-    imageUrl,
+    email: email ?? null,
+    imageUrl: imageUrl ?? null,
     emailVerified
-  }
+  } as Prisma.UserUncheckedCreateInput
 
   let user: User | null = null
-  let retry = 0
   let userCreated = false
-  // this function can run in parallel as such it is possible for multiple
-  // calls to reach this point and try to create the same user
-  // due to the earlier firebase async call.
+  // This can run in parallel; multiple calls may try to create the same user.
   try {
     user = await prisma.user.create({
-      data
+      data: createData
     })
     userCreated = true
-  } catch (e) {
-    do {
-      user = await prisma.user.update({
-        where: {
-          id: userId
-        },
-        data
-      })
-      retry++
-    } while (user == null && retry < 3)
+  } catch (createErr) {
+    // Create failed - often unique constraint (concurrent request already created). Fetch existing.
+    user = await prisma.user.findUnique({
+      ...query,
+      where: { userId }
+    })
+    if (user == null) throw createErr
   }
   // after user create so it is only sent once
   if (email != null && userCreated && !emailVerified)
diff --git a/apis/api-users/src/schema/user/inputs/index.ts b/apis/api-users/src/schema/user/inputs/index.ts
index 01a0068bf1b..cb9740480d4 100644
--- a/apis/api-users/src/schema/user/inputs/index.ts
+++ b/apis/api-users/src/schema/user/inputs/index.ts
@@ -1,5 +1,7 @@
 import './createVerificationRequestInput'
 import './meInput'
+import './mergeGuestInput'
 
 export { CreateVerificationRequestInput } from './createVerificationRequestInput'
 export { MeInput } from './meInput'
+export { MergeGuestInput } from './mergeGuestInput'
diff --git a/apis/api-users/src/schema/user/inputs/meInput.ts b/apis/api-users/src/schema/user/inputs/meInput.ts
index 1974a9f710f..3b015784a08 100644
--- a/apis/api-users/src/schema/user/inputs/meInput.ts
+++ b/apis/api-users/src/schema/user/inputs/meInput.ts
@@ -2,6 +2,7 @@ import { builder } from '../../builder'
 
 export const MeInput = builder.inputType('MeInput', {
   fields: (t) => ({
-    redirect: t.string({ required: false })
+    redirect: t.string({ required: false }),
+    createGuestIfAnonymous: t.boolean({ required: false })
   })
 })
diff --git a/apis/api-users/src/schema/user/objects/user.ts b/apis/api-users/src/schema/user/objects/user.ts
index adc67c1c1ed..a3b5fc78afc 100644
--- a/apis/api-users/src/schema/user/objects/user.ts
+++ b/apis/api-users/src/schema/user/objects/user.ts
@@ -3,6 +3,7 @@ import { builder } from '../../builder'
 export const User = builder.prismaObject('User', {
   fields: (t) => ({
     id: t.exposeID('id', { nullable: false }),
+    userId: t.exposeString('userId', { nullable: false }),
     firstName: t.field({
       type: 'String',
       nullable: false,
@@ -18,7 +19,7 @@ export const User = builder.prismaObject('User', {
       }
     }),
     lastName: t.exposeString('lastName'),
-    email: t.exposeString('email', { nullable: false }),
+    email: t.exposeString('email'),
     imageUrl: t.exposeString('imageUrl'),
     superAdmin: t.exposeBoolean('superAdmin'),
     emailVerified: t.exposeBoolean('emailVerified', { nullable: false })
diff --git a/apis/api-users/src/schema/user/user.spec.ts b/apis/api-users/src/schema/user/user.spec.ts
index 681b82aeca0..39f07f690d6 100644
--- a/apis/api-users/src/schema/user/user.spec.ts
+++ b/apis/api-users/src/schema/user/user.spec.ts
@@ -83,7 +83,12 @@ describe('api-users', () => {
       const data = await authClient({
         document: ME_QUERY
       })
-      expect(findOrFetchUser).toHaveBeenCalledWith({}, 'testUserId', undefined)
+      expect(findOrFetchUser).toHaveBeenCalledWith(
+        {},
+        'testUserId',
+        undefined,
+        { forceCreateForAnonymous: false }
+      )
       expect(data).toHaveProperty(
         'data.me',
         omit(user, ['createdAt', 'userId'])
diff --git a/apis/api-users/src/schema/user/user.ts b/apis/api-users/src/schema/user/user.ts
index 3b04e525fc0..7811eb2a3aa 100644
--- a/apis/api-users/src/schema/user/user.ts
+++ b/apis/api-users/src/schema/user/user.ts
@@ -6,7 +6,11 @@ import { impersonateUser } from '@core/yoga/firebaseClient'
 import { builder } from '../builder'
 
 import { findOrFetchUser } from './findOrFetchUser'
-import { CreateVerificationRequestInput, MeInput } from './inputs'
+import {
+  CreateVerificationRequestInput,
+  MeInput,
+  MergeGuestInput
+} from './inputs'
 import { User } from './objects'
 import { validateEmail } from './validateEmail'
 import { verifyUser } from './verifyUser'
@@ -57,11 +61,19 @@ builder.queryFields((t) => ({
       })
     },
     resolve: async (query, _parent, { input }, ctx) => {
-      return await findOrFetchUser(
-        query,
-        ctx.currentUser.id,
-        input?.redirect ?? undefined
-      )
+      try {
+        return await findOrFetchUser(
+          query,
+          ctx.currentUser.id,
+          input?.redirect ?? undefined,
+          { forceCreateForAnonymous: input?.createGuestIfAnonymous ?? false }
+        )
+      } catch (err) {
+        const message = err instanceof Error ? err.message : String(err)
+        throw new GraphQLError(message, {
+          extensions: { code: 'INTERNAL_SERVER_ERROR' }
+        })
+      }
     }
   }),
   user: t.withAuth({ isValidInterop: true }).prismaField({
@@ -92,6 +104,27 @@ builder.queryFields((t) => ({
 }))
 
 builder.mutationFields((t) => ({
+  mergeGuest: t.withAuth({ isAuthenticated: true }).prismaField({
+    type: 'User',
+    nullable: false,
+    args: {
+      input: t.arg({ type: MergeGuestInput, required: true })
+    },
+    resolve: async (query, _parent, { input }, ctx) => {
+      const userId = ctx.currentUser.id
+      const updated = await prisma.user.update({
+        ...query,
+        where: { userId },
+        data: {
+          firstName: input.firstName,
+          lastName: input.lastName,
+          email: input.email,
+          emailVerified: true
+        }
+      })
+      return updated
+    }
+  }),
   userImpersonate: t.withAuth({ isSuperAdmin: true }).field({
     type: 'String',
     args: {
@@ -151,6 +184,10 @@ builder.mutationFields((t) => ({
         throw new GraphQLError('User not found', {
           extensions: { code: 'NOT_FOUND' }
         })
+      if (user.email == null)
+        throw new GraphQLError('User not found', {
+          extensions: { code: 'NOT_FOUND' }
+        })
 
       const validatedEmail = await validateEmail(user.userId, user.email, token)
       if (!validatedEmail)
diff --git a/apps/journeys-admin/__generated__/GetCurrentUser.ts b/apps/journeys-admin/__generated__/GetCurrentUser.ts
index a5dc3ae8fb3..ca89840ceed 100644
--- a/apps/journeys-admin/__generated__/GetCurrentUser.ts
+++ b/apps/journeys-admin/__generated__/GetCurrentUser.ts
@@ -10,7 +10,11 @@
 export interface GetCurrentUser_me {
   __typename: "User";
   id: string;
-  email: string;
+  userId: string;
+  email: string | null;
+  firstName: string;
+  lastName: string | null;
+  emailVerified: boolean;
 }
 
 export interface GetCurrentUser {
diff --git a/apps/journeys-admin/__generated__/GetMe.ts b/apps/journeys-admin/__generated__/GetMe.ts
index e13fe28cfec..86395c650f2 100644
--- a/apps/journeys-admin/__generated__/GetMe.ts
+++ b/apps/journeys-admin/__generated__/GetMe.ts
@@ -14,7 +14,7 @@ export interface GetMe_me {
   id: string;
   firstName: string;
   lastName: string | null;
-  email: string;
+  email: string | null;
   imageUrl: string | null;
   superAdmin: boolean | null;
   emailVerified: boolean;
diff --git a/apps/journeys-admin/pages/api/login.tsx b/apps/journeys-admin/pages/api/login.tsx
index 46c5c3e943a..fe9e0dfb06d 100644
--- a/apps/journeys-admin/pages/api/login.tsx
+++ b/apps/journeys-admin/pages/api/login.tsx
@@ -13,6 +13,11 @@ export default async function handler(
     await setAuthCookies(req, res, {})
     res.status(200).json({ success: true })
   } catch (e) {
-    res.status(500).json({ error: 'Unexpected error.' })
+    console.error('Login API error:', e)
+    const message =
+      process.env.NODE_ENV !== 'production' && e instanceof Error
+        ? e.message
+        : 'Unexpected error.'
+    res.status(500).json({ error: message })
   }
 }
diff --git a/apps/journeys-admin/pages/templates/index.tsx b/apps/journeys-admin/pages/templates/index.tsx
index 00ae2733d9b..543769d2374 100644
--- a/apps/journeys-admin/pages/templates/index.tsx
+++ b/apps/journeys-admin/pages/templates/index.tsx
@@ -27,6 +27,7 @@ import { HelpScoutBeacon } from '../../src/components/HelpScoutBeacon'
 import { PageWrapper } from '../../src/components/PageWrapper'
 import { GET_ME } from '../../src/components/PageWrapper/NavigationDrawer/UserNavigation'
 import { initAndAuthApp } from '../../src/libs/initAndAuthApp'
+import { GuestUserTest } from '../../src/components/GuestUserTest/GuestUserTest'
 
 function TemplateIndexPage(): ReactElement {
   const { t } = useTranslation('apps-journeys-admin')
@@ -43,17 +44,19 @@ function TemplateIndexPage(): ReactElement {
   }, [user.id, query])
 
   const userSignedIn = user?.id != null
+  const isAnonymous = user.firebaseUser?.isAnonymous ?? false
+  const signedInNonAnonymous = userSignedIn && !isAnonymous
 
   return (
     <>
       <NextSeo title={t('Journey Templates')} />
       <PageWrapper
         title={t('Journey Templates')}
-        user={user}
+        user={signedInNonAnonymous ? user : undefined}
         mainBodyPadding={false}
         showMainHeader={false}
-        showAppHeader={userSignedIn}
-        showNavBar={userSignedIn}
+        showAppHeader={signedInNonAnonymous}
+        showNavBar={signedInNonAnonymous}
         fadeInNavBar
         backgroundColor="background.paper"
       >
@@ -78,6 +81,7 @@ function TemplateIndexPage(): ReactElement {
             px: { xs: 6, sm: 8, md: 10 }
           }}
         >
+          <GuestUserTest />
           <TemplateGallery />
         </Box>
       </PageWrapper>
diff --git a/apps/journeys-admin/src/components/GuestUserTest/GuestUserTest.tsx b/apps/journeys-admin/src/components/GuestUserTest/GuestUserTest.tsx
new file mode 100644
index 00000000000..5e6814907de
--- /dev/null
+++ b/apps/journeys-admin/src/components/GuestUserTest/GuestUserTest.tsx
@@ -0,0 +1,297 @@
+import { useEffect, useRef, useState } from 'react'
+
+import { gql, useMutation } from '@apollo/client'
+import Button from '@mui/material/Button'
+import Card from '@mui/material/Card'
+import CardContent from '@mui/material/CardContent'
+import CardHeader from '@mui/material/CardHeader'
+import Stack from '@mui/material/Stack'
+import Typography from '@mui/material/Typography'
+import { getApp } from 'firebase/app'
+import {
+  EmailAuthProvider,
+  getAuth,
+  linkWithCredential,
+  signInAnonymously,
+  updateProfile
+} from 'firebase/auth'
+import { useUser } from 'next-firebase-auth'
+
+import { JourneyProfileCreate } from '../../../__generated__/JourneyProfileCreate'
+import { useCurrentUserLazyQuery } from '../../libs/useCurrentUserLazyQuery'
+
+const JOURNEY_PROFILE_CREATE = gql`
+  mutation JourneyProfileCreate {
+    journeyProfileCreate {
+      id
+      userId
+      acceptedTermsAt
+    }
+  }
+`
+
+const MERGE_GUEST = gql`
+  mutation MergeGuest($input: MergeGuestInput!) {
+    mergeGuest(input: $input) {
+      id
+      userId
+      email
+      firstName
+      lastName
+      emailVerified
+    }
+  }
+`
+const count = 2
+
+const MERGE_GUEST_DISPLAY_NAME = 'John Doe'
+const MERGE_GUEST_EMAIL = `testemail${count}@example.com`
+const MERGE_GUEST_PASSWORD = 'MergeGuestTest1'
+
+export function GuestUserTest() {
+  const user = useUser()
+  const { loadUser, data: dbUser } = useCurrentUserLazyQuery()
+  const hasAttemptedAnonymousSignIn = useRef(false)
+  const [journeyProfileCreate] = useMutation<JourneyProfileCreate>(
+    JOURNEY_PROFILE_CREATE
+  )
+  const [mergeGuest] = useMutation(MERGE_GUEST)
+  const [isCreatingGuest, setIsCreatingGuest] = useState(false)
+  const [createGuestError, setCreateGuestError] = useState<string | null>(null)
+  const [isMergingGuest, setIsMergingGuest] = useState(false)
+  const [mergeGuestError, setMergeGuestError] = useState<string | null>(null)
+
+  // Current user: useUser() gives id, email, displayName, etc. When not signed in, user.id is null.
+  const currentUserId = user.id ?? null
+  const isSignedIn = currentUserId != null
+
+  // Anonymous check: firebaseUser is the Firebase JS SDK user (only set after client init).
+  // Firebase User has isAnonymous: https://firebase.google.com/docs/reference/js/auth.user#userisanonymous
+  const isAnonymous = user.firebaseUser?.isAnonymous ?? false
+
+  // When signed out and Firebase client is ready, sign in anonymously so we can show the anonymous ID.
+  useEffect(() => {
+    if (
+      !isSignedIn &&
+      user.clientInitialized &&
+      !hasAttemptedAnonymousSignIn.current
+    ) {
+      hasAttemptedAnonymousSignIn.current = true
+      signInAnonymously(getAuth(getApp())).catch(() => {
+        hasAttemptedAnonymousSignIn.current = false
+      })
+    }
+  }, [isSignedIn, user.clientInitialized])
+
+  useEffect(() => {
+    if (isSignedIn) {
+      loadUser()
+    }
+  }, [isSignedIn, loadUser])
+
+  function getErrorMessage(err: unknown, prefix: string): string {
+    if (err == null) return `${prefix}: Unknown error`
+    const apolloErr = err as {
+      message?: string
+      graphQLErrors?: Array<{ message?: string }>
+      networkError?: { message?: string; result?: { error?: string } }
+    }
+    const gqlMessage = apolloErr.graphQLErrors?.[0]?.message
+    const networkMessage =
+      apolloErr.networkError?.result?.error ?? apolloErr.networkError?.message
+    const message =
+      gqlMessage ?? networkMessage ?? apolloErr.message ?? String(err)
+    return `${prefix}: ${message}`
+  }
+
+  // Create guest: use me query with createGuestIfAnonymous (creates DB user via findOrFetchUser), then journey profile
+  const handleCreateGuest = async (): Promise<void> => {
+    setCreateGuestError(null)
+    setIsCreatingGuest(true)
+    try {
+      try {
+        await loadUser({
+          variables: { input: { createGuestIfAnonymous: true } }
+        })
+      } catch (err) {
+        setCreateGuestError(getErrorMessage(err, 'Create guest user'))
+        return
+      }
+      try {
+        await journeyProfileCreate()
+      } catch (err) {
+        setCreateGuestError(getErrorMessage(err, 'Create journey profile'))
+        return
+      }
+      try {
+        await loadUser()
+      } catch (err) {
+        setCreateGuestError(getErrorMessage(err, 'Load user'))
+      }
+    } finally {
+      setIsCreatingGuest(false)
+    }
+  }
+
+  const handleMergeGuest = async (): Promise<void> => {
+    setMergeGuestError(null)
+    setIsMergingGuest(true)
+    const auth = getAuth(getApp())
+    const firebaseUser = auth.currentUser
+    if (firebaseUser == null) {
+      setMergeGuestError('Merge guest: Not signed in')
+      setIsMergingGuest(false)
+      return
+    }
+    try {
+      await updateProfile(firebaseUser, {
+        displayName: MERGE_GUEST_DISPLAY_NAME
+      })
+    } catch (err) {
+      setMergeGuestError(getErrorMessage(err, 'Merge guest (Firebase profile)'))
+      setIsMergingGuest(false)
+      return
+    }
+    try {
+      const credential = EmailAuthProvider.credential(
+        MERGE_GUEST_EMAIL,
+        MERGE_GUEST_PASSWORD
+      )
+      await linkWithCredential(firebaseUser, credential)
+    } catch (err) {
+      setMergeGuestError(
+        getErrorMessage(err, 'Merge guest (Firebase email link)')
+      )
+      setIsMergingGuest(false)
+      return
+    }
+    try {
+      await mergeGuest({
+        variables: {
+          input: {
+            firstName: 'John',
+            lastName: 'Doe',
+            email: MERGE_GUEST_EMAIL
+          }
+        }
+      })
+    } catch (err) {
+      setMergeGuestError(getErrorMessage(err, 'Merge guest (DB)'))
+      setIsMergingGuest(false)
+      return
+    }
+    try {
+      await loadUser()
+    } catch (err) {
+      setMergeGuestError(getErrorMessage(err, 'Merge guest (reload)'))
+    } finally {
+      setIsMergingGuest(false)
+    }
+  }
+
+  const displayName =
+    dbUser != null && (dbUser.firstName || dbUser.lastName)
+      ? [dbUser.firstName, dbUser.lastName].filter(Boolean).join(' ')
+      : null
+
+  return (
+    <Stack gap={2} sx={{ border: '2px solid green', p: 4, mt: 4 }}>
+      <Typography variant="h1">Guest User Test</Typography>
+      <Stack gap={2} direction="row" flexWrap="wrap">
+        <Card variant="outlined" sx={{ border: '2px solid orange' }}>
+          <CardHeader
+            title="Firebase user"
+            subheader="Current auth state from Firebase"
+            titleTypographyProps={{ variant: 'subtitle1' }}
+          />
+          <CardContent>
+            <Stack gap={1}>
+              {currentUserId != null && (
+                <Typography variant="body2" color="text.secondary">
+                  {isAnonymous ? 'Anonymous ID' : 'UID'}: {currentUserId}
+                </Typography>
+              )}
+              {user.email != null && user.email !== '' && (
+                <Typography variant="body2" color="text.secondary">
+                  Email: {user.email}
+                </Typography>
+              )}
+              <Typography variant="body2" color="text.secondary">
+                Signed in: {isSignedIn ? 'Yes' : 'No'}
+              </Typography>
+              <Typography variant="body2" color="text.secondary">
+                Anonymous: {isAnonymous ? 'Yes' : 'No'}
+              </Typography>
+            </Stack>
+          </CardContent>
+        </Card>
+        <Card variant="outlined" sx={{ border: '2px solid blue' }}>
+          <CardHeader
+            title="Database user"
+            subheader="User record from the database"
+            titleTypographyProps={{ variant: 'subtitle1' }}
+          />
+          <CardContent>
+            <Stack gap={1}>
+              {dbUser != null && dbUser.userId !== '' ? (
+                <>
+                  <Typography variant="body2" color="text.secondary">
+                    User ID: {dbUser.userId}
+                  </Typography>
+                  {dbUser.email != null && dbUser.email !== '' && (
+                    <Typography variant="body2" color="text.secondary">
+                      Email: {dbUser.email}
+                    </Typography>
+                  )}
+                  {displayName != null && (
+                    <Typography variant="body2" color="text.secondary">
+                      Name: {displayName}
+                    </Typography>
+                  )}
+                  <Typography variant="body2" color="text.secondary">
+                    Email verified: {dbUser.emailVerified ? 'Yes' : 'No'}
+                  </Typography>
+                </>
+              ) : (
+                <Typography variant="body2" color="text.secondary">
+                  {!isSignedIn
+                    ? 'Sign in to see database user'
+                    : isAnonymous
+                      ? 'No database user (anonymous only)'
+                      : 'Loading…'}
+                </Typography>
+              )}
+            </Stack>
+          </CardContent>
+        </Card>
+      </Stack>
+
+      <Stack direction="row" spacing={2} sx={{ mt: 2 }}>
+        <Button
+          variant="outlined"
+          onClick={() => void handleCreateGuest()}
+          disabled={isCreatingGuest}
+        >
+          {isCreatingGuest ? 'Creating…' : 'Create Guest'}
+        </Button>
+        <Button
+          variant="outlined"
+          onClick={() => void handleMergeGuest()}
+          disabled={isMergingGuest}
+        >
+          {isMergingGuest ? 'Merging…' : 'Merge Guest'}
+        </Button>
+      </Stack>
+      {createGuestError != null && (
+        <Typography variant="body2" color="error">
+          {createGuestError}
+        </Typography>
+      )}
+      {mergeGuestError != null && (
+        <Typography variant="body2" color="error">
+          {mergeGuestError}
+        </Typography>
+      )}
+    </Stack>
+  )
+}
diff --git a/apps/journeys-admin/src/components/SignIn/RegisterPage/RegisterPage.tsx b/apps/journeys-admin/src/components/SignIn/RegisterPage/RegisterPage.tsx
index e51ac5d10e5..ef203f14751 100644
--- a/apps/journeys-admin/src/components/SignIn/RegisterPage/RegisterPage.tsx
+++ b/apps/journeys-admin/src/components/SignIn/RegisterPage/RegisterPage.tsx
@@ -6,28 +6,83 @@ import InputAdornment from '@mui/material/InputAdornment'
 import Stack from '@mui/material/Stack'
 import TextField from '@mui/material/TextField'
 import Typography from '@mui/material/Typography'
+import { gql, useMutation } from '@apollo/client'
+import { getApp } from 'firebase/app'
 import {
   createUserWithEmailAndPassword,
+  EmailAuthProvider,
   getAuth,
+  linkWithCredential,
   signInWithEmailAndPassword,
   updateProfile
 } from 'firebase/auth'
 import { Form, Formik } from 'formik'
 import { useRouter } from 'next/router'
 import { useTranslation } from 'next-i18next'
-import React, { ReactElement } from 'react'
+import { useUser } from 'next-firebase-auth'
+import React, { ReactElement, useState } from 'react'
 import { InferType, object, string } from 'yup'
 
+import { useCurrentUserLazyQuery } from '../../../libs/useCurrentUserLazyQuery'
 import { useHandleNewAccountRedirect } from '../../../libs/useRedirectNewAccount'
 import { PageProps } from '../types'
 
+const MERGE_GUEST = gql`
+  mutation MergeGuest($input: MergeGuestInput!) {
+    mergeGuest(input: $input) {
+      id
+      userId
+      email
+      firstName
+      lastName
+      emailVerified
+    }
+  }
+`
+
+function parseNameToFirstAndLast(name: string): {
+  firstName: string
+  lastName: string
+} {
+  const trimmed = name.trim()
+  if (trimmed === '') return { firstName: '', lastName: '' }
+  const parts = trimmed.split(/\s+/).filter(Boolean)
+  if (parts.length === 0) return { firstName: '', lastName: '' }
+  if (parts.length === 1) return { firstName: parts[0], lastName: '' }
+  return {
+    firstName: parts[0],
+    lastName: parts.slice(1).join(' ')
+  }
+}
+
+function getErrorMessage(err: unknown, prefix: string): string {
+  if (err == null) return `${prefix}: Unknown error`
+  const apolloErr = err as {
+    message?: string
+    graphQLErrors?: Array<{ message?: string }>
+    networkError?: { message?: string; result?: { error?: string } }
+  }
+  const gqlMessage = apolloErr.graphQLErrors?.[0]?.message
+  const networkMessage =
+    apolloErr.networkError?.result?.error ?? apolloErr.networkError?.message
+  const message =
+    gqlMessage ?? networkMessage ?? apolloErr.message ?? String(err)
+  return `${prefix}: ${message}`
+}
+
 export function RegisterPage({
   setActivePage,
   userEmail
 }: PageProps): ReactElement {
   const { t } = useTranslation('apps-journeys-admin')
   const [showPassword, setShowPassword] = React.useState(false)
+  const [submitError, setSubmitError] = useState<string | null>(null)
   const router = useRouter()
+  const user = useUser()
+  const [mergeGuest] = useMutation(MERGE_GUEST)
+  const { loadUser } = useCurrentUserLazyQuery()
+
+  const isAnonymous = user.firebaseUser?.isAnonymous ?? false
 
   useHandleNewAccountRedirect()
 
@@ -72,21 +127,95 @@ export function RegisterPage({
     await signInWithEmailAndPassword(auth, email, password)
   }
 
+  async function mergeGuestAndSignIn(
+    email: string,
+    name: string,
+    password: string,
+    setFieldError: (field: string, message: string) => void,
+    setSubmitting: (isSubmitting: boolean) => void
+  ): Promise<void> {
+    const auth = getAuth(getApp())
+    const firebaseUser = auth.currentUser
+    if (firebaseUser == null) {
+      setSubmitError(t('Not signed in. Please try again.'))
+      setSubmitting(false)
+      return
+    }
+    try {
+      await updateProfile(firebaseUser, { displayName: name })
+    } catch (err) {
+      setSubmitError(getErrorMessage(err, t('Update profile')))
+      setSubmitting(false)
+      return
+    }
+    try {
+      const credential = EmailAuthProvider.credential(email, password)
+      await linkWithCredential(firebaseUser, credential)
+    } catch (err) {
+      const errCode = (err as { code?: string })?.code
+      if (errCode === 'auth/email-already-in-use') {
+        setFieldError(
+          'email',
+          t('The email address is already used by another account')
+        )
+      } else {
+        setSubmitError(getErrorMessage(err, t('Link account')))
+      }
+      setSubmitting(false)
+      return
+    }
+    const { firstName, lastName } = parseNameToFirstAndLast(name)
+    try {
+      await mergeGuest({
+        variables: {
+          input: { firstName, lastName, email }
+        }
+      })
+    } catch (err) {
+      setSubmitError(getErrorMessage(err, t('Save account')))
+      setSubmitting(false)
+      return
+    }
+    try {
+      await loadUser()
+    } catch (err) {
+      setSubmitError(getErrorMessage(err, t('Reload user')))
+    } finally {
+      setSubmitting(false)
+    }
+  }
+
   async function handleCreateAccount(
     values: InferType<typeof validationSchema>,
-    { setFieldError }
+    { setFieldError, setSubmitting }
   ): Promise<void> {
+    setSubmitError(null)
     try {
-      await createAccountAndSignIn(values.email, values.name, values.password)
+      if (isAnonymous) {
+        await mergeGuestAndSignIn(
+          values.email,
+          values.name,
+          values.password,
+          setFieldError,
+          setSubmitting
+        )
+      } else {
+        await createAccountAndSignIn(values.email, values.name, values.password)
+      }
     } catch (error) {
-      if (error.code === 'auth/email-already-in-use') {
+      const errCode = (error as { code?: string })?.code
+      if (errCode === 'auth/email-already-in-use') {
         setFieldError(
           'email',
           t('The email address is already used by another account')
         )
       } else {
+        setSubmitError(
+          error instanceof Error ? error.message : t('Something went wrong')
+        )
         console.error(error)
       }
+      setSubmitting(false)
     }
   }
   return (
@@ -110,6 +239,11 @@ export function RegisterPage({
               <Typography variant="h6" textAlign="left" sx={{ mb: 2 }}>
                 {t('Create account')}
               </Typography>
+              {submitError != null && (
+                <Typography variant="body2" color="error">
+                  {submitError}
+                </Typography>
+              )}
               <TextField
                 id="name"
                 autoComplete="name"
diff --git a/apps/journeys-admin/src/libs/useCurrentUserLazyQuery/useCurrentUser.spec.tsx b/apps/journeys-admin/src/libs/useCurrentUserLazyQuery/useCurrentUser.spec.tsx
index ea0121e0f28..78412412fa3 100644
--- a/apps/journeys-admin/src/libs/useCurrentUserLazyQuery/useCurrentUser.spec.tsx
+++ b/apps/journeys-admin/src/libs/useCurrentUserLazyQuery/useCurrentUser.spec.tsx
@@ -19,8 +19,13 @@ describe('useCurrentUserLazyQuery', () => {
               result: {
                 data: {
                   me: {
+                    __typename: 'User',
                     id: 'user.id',
-                    email: 'test@email.com'
+                    userId: 'firebase-uid-123',
+                    email: 'test@email.com',
+                    firstName: 'Test',
+                    lastName: 'User',
+                    emailVerified: true
                   }
                 }
               }
@@ -38,8 +43,13 @@ describe('useCurrentUserLazyQuery', () => {
 
     await waitFor(() =>
       expect(result.current.data).toEqual({
+        __typename: 'User',
         id: 'user.id',
-        email: 'test@email.com'
+        userId: 'firebase-uid-123',
+        email: 'test@email.com',
+        firstName: 'Test',
+        lastName: 'User',
+        emailVerified: true
       })
     )
   })
@@ -56,8 +66,13 @@ describe('useCurrentUserLazyQuery', () => {
               result: {
                 data: {
                   me: {
+                    __typename: 'User',
                     id: 'user.id',
-                    email: 'test@email.com'
+                    userId: 'firebase-uid-123',
+                    email: 'test@email.com',
+                    firstName: 'Test',
+                    lastName: 'User',
+                    emailVerified: true
                   }
                 }
               }
@@ -72,7 +87,11 @@ describe('useCurrentUserLazyQuery', () => {
     expect(result.current.data).toEqual({
       __typename: 'User',
       id: '',
-      email: ''
+      userId: '',
+      email: null,
+      firstName: '',
+      lastName: null,
+      emailVerified: false
     })
   })
 })
diff --git a/apps/journeys-admin/src/libs/useCurrentUserLazyQuery/useCurrentUserLazyQuery.mock.ts b/apps/journeys-admin/src/libs/useCurrentUserLazyQuery/useCurrentUserLazyQuery.mock.ts
index dd8bfad7514..21a35edd73f 100644
--- a/apps/journeys-admin/src/libs/useCurrentUserLazyQuery/useCurrentUserLazyQuery.mock.ts
+++ b/apps/journeys-admin/src/libs/useCurrentUserLazyQuery/useCurrentUserLazyQuery.mock.ts
@@ -13,7 +13,11 @@ export const mockUseCurrentUserLazyQuery: MockedResponse<GetCurrentUser> = {
       me: {
         __typename: 'User',
         id: 'user.id',
-        email: 'test@email.com'
+        userId: 'firebase-uid-123',
+        email: 'test@email.com',
+        firstName: 'Test',
+        lastName: 'User',
+        emailVerified: true
       }
     }
   }
diff --git a/apps/journeys-admin/src/libs/useCurrentUserLazyQuery/useCurrentUserLazyQuery.ts b/apps/journeys-admin/src/libs/useCurrentUserLazyQuery/useCurrentUserLazyQuery.ts
index f78251e6b17..a16954a5469 100644
--- a/apps/journeys-admin/src/libs/useCurrentUserLazyQuery/useCurrentUserLazyQuery.ts
+++ b/apps/journeys-admin/src/libs/useCurrentUserLazyQuery/useCurrentUserLazyQuery.ts
@@ -11,10 +11,14 @@ import {
 } from '../../../__generated__/GetCurrentUser'
 
 export const GET_CURRENT_USER = gql`
-  query GetCurrentUser {
-    me {
+  query GetCurrentUser($input: MeInput) {
+    me(input: $input) {
       id
+      userId
       email
+      firstName
+      lastName
+      emailVerified
     }
   }
 `
@@ -29,5 +33,16 @@ export function useCurrentUserLazyQuery(): {
     return { loadUser, data: data.me }
   }
 
-  return { loadUser, data: { __typename: 'User', id: '', email: '' } }
+  return {
+    loadUser,
+    data: {
+      __typename: 'User',
+      id: '',
+      userId: '',
+      email: null,
+      firstName: '',
+      lastName: null,
+      emailVerified: false
+    }
+  }
 }
diff --git a/libs/prisma/users/db/migrations/20250201120000_make_user_email_nullable/migration.sql b/libs/prisma/users/db/migrations/20250201120000_make_user_email_nullable/migration.sql
new file mode 100644
index 00000000000..f5908591047
--- /dev/null
+++ b/libs/prisma/users/db/migrations/20250201120000_make_user_email_nullable/migration.sql
@@ -0,0 +1,2 @@
+-- AlterTable
+ALTER TABLE "User" ALTER COLUMN "email" DROP NOT NULL;
diff --git a/libs/prisma/users/db/schema.prisma b/libs/prisma/users/db/schema.prisma
index 7647ef9a255..44820f4e454 100644
--- a/libs/prisma/users/db/schema.prisma
+++ b/libs/prisma/users/db/schema.prisma
@@ -29,7 +29,7 @@ model User {
   userId        String   @unique
   firstName     String
   lastName      String?
-  email         String   @unique
+  email         String?  @unique
   imageUrl      String?
   createdAt     DateTime @default(now())
   superAdmin    Boolean  @default(false)