diff --git a/CHANGES.md b/CHANGES.md
index 1a684ee56f..3362588cf8 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -19,6 +19,7 @@ Improvements 🙌:
  - Fix quick click action (#3127)
  - Get Event after a Push for a faster notification display in some conditions
  - Always try to retry Http requests in case of 429 (#1300)
+ - registration availability endpoint added to matrix-sdk
 
 Bugfix 🐛:
  - Fix bad theme change for the MainActivity
diff --git a/matrix-sdk-android/src/main/java/org/matrix/android/sdk/api/auth/registration/RegistrationAvailability.kt b/matrix-sdk-android/src/main/java/org/matrix/android/sdk/api/auth/registration/RegistrationAvailability.kt
new file mode 100644
index 0000000000..f9a7ace7ba
--- /dev/null
+++ b/matrix-sdk-android/src/main/java/org/matrix/android/sdk/api/auth/registration/RegistrationAvailability.kt
@@ -0,0 +1,24 @@
+/*
+ * Copyright 2021 The Matrix.org Foundation C.I.C.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.matrix.android.sdk.api.auth.registration
+
+import org.matrix.android.sdk.api.failure.Failure
+
+sealed class RegistrationAvailability {
+    object Available : RegistrationAvailability()
+    data class NotAvailable(val failure: Failure.ServerError) : RegistrationAvailability()
+}
diff --git a/matrix-sdk-android/src/main/java/org/matrix/android/sdk/api/auth/registration/RegistrationWizard.kt b/matrix-sdk-android/src/main/java/org/matrix/android/sdk/api/auth/registration/RegistrationWizard.kt
index d00c9a0c82..38a5a77291 100644
--- a/matrix-sdk-android/src/main/java/org/matrix/android/sdk/api/auth/registration/RegistrationWizard.kt
+++ b/matrix-sdk-android/src/main/java/org/matrix/android/sdk/api/auth/registration/RegistrationWizard.kt
@@ -36,6 +36,8 @@ interface RegistrationWizard {
 
     suspend fun checkIfEmailHasBeenValidated(delayMillis: Long): RegistrationResult
 
+    suspend fun registrationAvailable(userName: String): RegistrationAvailability
+
     val currentThreePid: String?
 
     // True when login and password has been sent with success to the homeserver
diff --git a/matrix-sdk-android/src/main/java/org/matrix/android/sdk/api/failure/Extensions.kt b/matrix-sdk-android/src/main/java/org/matrix/android/sdk/api/failure/Extensions.kt
index 17362ff8d7..0ba61e5890 100644
--- a/matrix-sdk-android/src/main/java/org/matrix/android/sdk/api/failure/Extensions.kt
+++ b/matrix-sdk-android/src/main/java/org/matrix/android/sdk/api/failure/Extensions.kt
@@ -65,13 +65,16 @@ fun Throwable.isInvalidUIAAuth(): Boolean {
  * Try to convert to a RegistrationFlowResponse. Return null in the cases it's not possible
  */
 fun Throwable.toRegistrationFlowResponse(): RegistrationFlowResponse? {
-    return if (this is Failure.OtherServerError && httpCode == 401) {
+    return if (this is Failure.OtherServerError
+            && httpCode == HttpsURLConnection.HTTP_UNAUTHORIZED /* 401 */) {
         tryOrNull {
             MoshiProvider.providesMoshi()
                     .adapter(RegistrationFlowResponse::class.java)
                     .fromJson(errorBody)
         }
-    } else if (this is Failure.ServerError && httpCode == 401 && error.code == MatrixError.M_FORBIDDEN) {
+    } else if (this is Failure.ServerError
+            && httpCode == HttpsURLConnection.HTTP_UNAUTHORIZED /* 401 */
+            && error.code == MatrixError.M_FORBIDDEN) {
         // This happens when the submission for this stage was bad (like bad password)
         if (error.session != null && error.flows != null) {
             RegistrationFlowResponse(
@@ -87,3 +90,11 @@ fun Throwable.toRegistrationFlowResponse(): RegistrationFlowResponse? {
         null
     }
 }
+
+fun Throwable.isRegistrationAvailabilityError(): Boolean {
+    return this is Failure.ServerError
+            && httpCode == HttpsURLConnection.HTTP_BAD_REQUEST /* 400 */
+            && (error.code == MatrixError.M_USER_IN_USE
+            || error.code == MatrixError.M_INVALID_USERNAME
+            || error.code == MatrixError.M_EXCLUSIVE)
+}
diff --git a/matrix-sdk-android/src/main/java/org/matrix/android/sdk/internal/auth/AuthAPI.kt b/matrix-sdk-android/src/main/java/org/matrix/android/sdk/internal/auth/AuthAPI.kt
index 2ce5c67a94..f93f285c6e 100644
--- a/matrix-sdk-android/src/main/java/org/matrix/android/sdk/internal/auth/AuthAPI.kt
+++ b/matrix-sdk-android/src/main/java/org/matrix/android/sdk/internal/auth/AuthAPI.kt
@@ -17,6 +17,7 @@
 package org.matrix.android.sdk.internal.auth
 
 import org.matrix.android.sdk.api.auth.data.Credentials
+import org.matrix.android.sdk.internal.auth.data.Availability
 import org.matrix.android.sdk.internal.auth.data.LoginFlowResponse
 import org.matrix.android.sdk.internal.auth.data.PasswordLoginParams
 import org.matrix.android.sdk.internal.auth.data.RiotConfig
@@ -34,6 +35,7 @@ import retrofit2.http.GET
 import retrofit2.http.Headers
 import retrofit2.http.POST
 import retrofit2.http.Path
+import retrofit2.http.Query
 import retrofit2.http.Url
 
 /**
@@ -65,6 +67,12 @@ internal interface AuthAPI {
     @POST(NetworkConstants.URI_API_PREFIX_PATH_R0 + "register")
     suspend fun register(@Body registrationParams: RegistrationParams): Credentials
 
+    /**
+     * Checks to see if a username is available, and valid, for the server.
+     */
+    @GET(NetworkConstants.URI_API_PREFIX_PATH_R0 + "register/available")
+    suspend fun registerAvailable(@Query("username") username: String): Availability
+
     /**
      * Add 3Pid during registration
      * Ref: https://gist.github.com/jryans/839a09bf0c5a70e2f36ed990d50ed928
diff --git a/matrix-sdk-android/src/main/java/org/matrix/android/sdk/internal/auth/data/Availability.kt b/matrix-sdk-android/src/main/java/org/matrix/android/sdk/internal/auth/data/Availability.kt
new file mode 100644
index 0000000000..5ef3c0d06a
--- /dev/null
+++ b/matrix-sdk-android/src/main/java/org/matrix/android/sdk/internal/auth/data/Availability.kt
@@ -0,0 +1,29 @@
+/*
+ * Copyright 2021 The Matrix.org Foundation C.I.C.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.matrix.android.sdk.internal.auth.data
+
+import com.squareup.moshi.Json
+import com.squareup.moshi.JsonClass
+
+@JsonClass(generateAdapter = true)
+internal data class Availability(
+        /**
+         * A flag to indicate that the username is available. This should always be true when the server replies with 200 OK.
+         */
+        @Json(name = "available")
+        val available: Boolean? = null
+)
diff --git a/matrix-sdk-android/src/main/java/org/matrix/android/sdk/internal/auth/registration/DefaultRegistrationWizard.kt b/matrix-sdk-android/src/main/java/org/matrix/android/sdk/internal/auth/registration/DefaultRegistrationWizard.kt
index 91e414e689..4a3d53a8fc 100644
--- a/matrix-sdk-android/src/main/java/org/matrix/android/sdk/internal/auth/registration/DefaultRegistrationWizard.kt
+++ b/matrix-sdk-android/src/main/java/org/matrix/android/sdk/internal/auth/registration/DefaultRegistrationWizard.kt
@@ -19,6 +19,7 @@ package org.matrix.android.sdk.internal.auth.registration
 import kotlinx.coroutines.delay
 import org.matrix.android.sdk.api.auth.data.LoginFlowTypes
 import org.matrix.android.sdk.api.auth.registration.RegisterThreePid
+import org.matrix.android.sdk.api.auth.registration.RegistrationAvailability
 import org.matrix.android.sdk.api.auth.registration.RegistrationResult
 import org.matrix.android.sdk.api.auth.registration.RegistrationWizard
 import org.matrix.android.sdk.api.auth.registration.toFlowResult
@@ -40,9 +41,10 @@ internal class DefaultRegistrationWizard(
 
     private var pendingSessionData: PendingSessionData = pendingSessionStore.getPendingSessionData() ?: error("Pending session data should exist here")
 
-    private val registerTask = DefaultRegisterTask(authAPI)
-    private val registerAddThreePidTask = DefaultRegisterAddThreePidTask(authAPI)
-    private val validateCodeTask = DefaultValidateCodeTask(authAPI)
+    private val registerTask: RegisterTask = DefaultRegisterTask(authAPI)
+    private val registerAvailableTask: RegisterAvailableTask = DefaultRegisterAvailableTask(authAPI)
+    private val registerAddThreePidTask: RegisterAddThreePidTask = DefaultRegisterAddThreePidTask(authAPI)
+    private val validateCodeTask: ValidateCodeTask = DefaultValidateCodeTask(authAPI)
 
     override val currentThreePid: String?
         get() {
@@ -203,4 +205,8 @@ internal class DefaultRegistrationWizard(
         val session = sessionCreator.createSession(credentials, pendingSessionData.homeServerConnectionConfig)
         return RegistrationResult.Success(session)
     }
+
+    override suspend fun registrationAvailable(userName: String): RegistrationAvailability {
+        return registerAvailableTask.execute(RegisterAvailableTask.Params(userName))
+    }
 }
diff --git a/matrix-sdk-android/src/main/java/org/matrix/android/sdk/internal/auth/registration/RegisterAvailableTask.kt b/matrix-sdk-android/src/main/java/org/matrix/android/sdk/internal/auth/registration/RegisterAvailableTask.kt
new file mode 100644
index 0000000000..314a24dad4
--- /dev/null
+++ b/matrix-sdk-android/src/main/java/org/matrix/android/sdk/internal/auth/registration/RegisterAvailableTask.kt
@@ -0,0 +1,47 @@
+/*
+ * Copyright 2021 The Matrix.org Foundation C.I.C.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.matrix.android.sdk.internal.auth.registration
+
+import org.matrix.android.sdk.api.auth.registration.RegistrationAvailability
+import org.matrix.android.sdk.api.failure.Failure
+import org.matrix.android.sdk.api.failure.isRegistrationAvailabilityError
+import org.matrix.android.sdk.internal.auth.AuthAPI
+import org.matrix.android.sdk.internal.network.executeRequest
+import org.matrix.android.sdk.internal.task.Task
+
+internal interface RegisterAvailableTask : Task<RegisterAvailableTask.Params, RegistrationAvailability> {
+    data class Params(
+            val userName: String
+    )
+}
+
+internal class DefaultRegisterAvailableTask(private val authAPI: AuthAPI) : RegisterAvailableTask {
+    override suspend fun execute(params: RegisterAvailableTask.Params): RegistrationAvailability {
+        return try {
+            executeRequest(null) {
+                authAPI.registerAvailable(params.userName)
+            }
+            RegistrationAvailability.Available
+        } catch (exception: Throwable) {
+            if (exception.isRegistrationAvailabilityError()) {
+                RegistrationAvailability.NotAvailable(exception as Failure.ServerError)
+            } else {
+                throw exception
+            }
+        }
+    }
+}