diff --git a/api/src/routes/helpers/is-restricted.ts b/api/src/routes/helpers/is-restricted.ts
new file mode 100644
index 00000000000..6e843a64718
--- /dev/null
+++ b/api/src/routes/helpers/is-restricted.ts
@@ -0,0 +1,12 @@
+import { isProfane } from 'no-profanity';
+
+import { blocklistedUsernames } from '../../../../shared/config/constants';
+
+/**
+ * Checks if a username is restricted (i.e. It's profane or reserved).
+ * @param username - The username to check.
+ * @returns True if the username is restricted, false otherwise.
+ */
+export const isRestricted = (username: string): boolean => {
+  return isProfane(username) || blocklistedUsernames.includes(username);
+};
diff --git a/api/src/routes/settings.ts b/api/src/routes/settings.ts
index 1a0290e0285..44d975c844c 100644
--- a/api/src/routes/settings.ts
+++ b/api/src/routes/settings.ts
@@ -14,13 +14,12 @@ import type {
 } from 'fastify';
 import { ResolveFastifyReplyType } from 'fastify/types/type-provider';
 import { differenceInMinutes } from 'date-fns';
-import { isProfane } from 'no-profanity';
 
-import { blocklistedUsernames } from '../../../shared/config/constants';
 import { isValidUsername } from '../../../shared/utils/validate';
 import * as schemas from '../schemas';
 import { createAuthToken } from '../utils/tokens';
 import { API_LOCATION } from '../utils/env';
+import { isRestricted } from './helpers/is-restricted';
 
 type WaitMesssageArgs = {
   sentAt: Date | null;
@@ -401,9 +400,6 @@ ${isLinkSentWithinLimitTTL}`
           });
         }
 
-        const isUserNameProfane = isProfane(newUsername);
-        const onBlocklist = blocklistedUsernames.includes(newUsername);
-
         const usernameTaken =
           newUsername === oldUsername
             ? false
@@ -411,7 +407,7 @@ ${isLinkSentWithinLimitTTL}`
                 where: { username: newUsername }
               });
 
-        if (usernameTaken || isUserNameProfane || onBlocklist) {
+        if (usernameTaken || isRestricted(newUsername)) {
           void reply.code(400);
           return reply.send({
             message: 'flash.username-taken',
diff --git a/api/src/routes/user.test.ts b/api/src/routes/user.test.ts
index deaaa579e91..bcf9dfac8d8 100644
--- a/api/src/routes/user.test.ts
+++ b/api/src/routes/user.test.ts
@@ -1286,6 +1286,56 @@ Thanks and regards,
         });
       });
     });
+    describe('GET /api/users/exists', () => {
+      beforeAll(async () => {
+        await fastifyTestInstance.prisma.user.create({
+          data: minimalUserData
+        });
+      });
+
+      it('should return { exists: true } with a 400 status code if the username param is missing or empty', async () => {
+        const res = await superGet('/api/users/exists');
+
+        expect(res.body).toStrictEqual({ exists: true });
+        expect(res.statusCode).toBe(400);
+
+        const res2 = await superGet('/api/users/exists?username=');
+
+        expect(res2.body).toStrictEqual({ exists: true });
+        expect(res2.statusCode).toBe(400);
+      });
+
+      it('should return { exists: true } if the username exists', async () => {
+        const res = await superGet('/api/users/exists?username=testuser');
+
+        expect(res.body).toStrictEqual({ exists: true });
+        expect(res.statusCode).toBe(200);
+      });
+
+      it('should ignore case when checking for username existence', async () => {
+        const res = await superGet('/api/users/exists?username=TeStUsEr');
+
+        expect(res.body).toStrictEqual({ exists: true });
+        expect(res.statusCode).toBe(200);
+      });
+
+      it('should return { exists: false } if the username does not exist', async () => {
+        const res = await superGet('/api/users/exists?username=nonexistent');
+
+        expect(res.body).toStrictEqual({ exists: false });
+        expect(res.statusCode).toBe(200);
+      });
+
+      it('should return { exists: true } if the username is restricted (ignoring case)', async () => {
+        const res = await superGet('/api/users/exists?username=pRofIle');
+
+        expect(res.body).toStrictEqual({ exists: true });
+
+        const res2 = await superGet('/api/users/exists?username=flAnge');
+
+        expect(res2.body).toStrictEqual({ exists: true });
+      });
+    });
   });
 });
 
diff --git a/api/src/routes/user.ts b/api/src/routes/user.ts
index 9004df1c884..9e9d4a9e992 100644
--- a/api/src/routes/user.ts
+++ b/api/src/routes/user.ts
@@ -27,6 +27,7 @@ import { trimTags } from '../utils/validation';
 import { generateReportEmail } from '../utils/email-templates';
 import { createResetProperties } from '../utils/create-user';
 import { challengeTypes } from '../../../shared/config/challenge-types';
+import { isRestricted } from './helpers/is-restricted';
 
 // user flags that the api-server returns as false if they're missing in the
 // user document. Since Prisma returns null for missing fields, we need to
@@ -786,5 +787,32 @@ export const userPublicGetRoutes: FastifyPluginCallbackTypebox = (
     }
   );
 
+  fastify.get(
+    '/api/users/exists',
+    {
+      schema: schemas.userExists,
+      attachValidation: true
+    },
+    async (req, reply) => {
+      if (req.validationError) {
+        void reply.code(400);
+        // TODO(Post-MVP): return a message telling the requester that their
+        // request was malformed.
+        return await reply.send({ exists: true });
+      }
+
+      const username = req.query.username.toLowerCase();
+
+      if (isRestricted(username)) return await reply.send({ exists: true });
+
+      const exists =
+        (await fastify.prisma.user.count({
+          where: { username }
+        })) > 0;
+
+      await reply.send({ exists });
+    }
+  );
+
   done();
 };
diff --git a/api/src/schemas.ts b/api/src/schemas.ts
index 6a12c08d4aa..d322e502fc1 100644
--- a/api/src/schemas.ts
+++ b/api/src/schemas.ts
@@ -1,4 +1,5 @@
 export { getPublicProfile } from './schemas/api/users/get-public-profile';
+export { userExists } from './schemas/api/users/exists';
 export { certSlug } from './schemas/certificate/cert-slug';
 export { certificateVerify } from './schemas/certificate/certificate-verify';
 export { backendChallengeCompleted } from './schemas/challenge/backend-challenge-completed';
diff --git a/api/src/schemas/api/users/exists.ts b/api/src/schemas/api/users/exists.ts
new file mode 100644
index 00000000000..0416d3ff28e
--- /dev/null
+++ b/api/src/schemas/api/users/exists.ts
@@ -0,0 +1,15 @@
+import { Type } from '@fastify/type-provider-typebox';
+
+export const userExists = {
+  querystring: Type.Object({
+    username: Type.String({ minLength: 1 })
+  }),
+  response: {
+    200: Type.Object({
+      exists: Type.Boolean()
+    }),
+    400: Type.Object({
+      exists: Type.Literal(true)
+    })
+  }
+};