diff --git a/matrix-sdk-android/src/main/java/org/matrix/android/sdk/api/auth/data/Availability.kt b/matrix-sdk-android/src/main/java/org/matrix/android/sdk/api/auth/data/Availability.kt
new file mode 100644
index 0000000000..3fbbdd161f
--- /dev/null
+++ b/matrix-sdk-android/src/main/java/org/matrix/android/sdk/api/auth/data/Availability.kt
@@ -0,0 +1,26 @@
+/*
+ * Copyright 2020 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.data
+
+import com.squareup.moshi.Json
+import com.squareup.moshi.JsonClass
+
+@JsonClass(generateAdapter = true)
+data class Availability(
+    @Json(name = "available")
+    val available: Boolean
+)
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..7c7d769a35
--- /dev/null
+++ b/matrix-sdk-android/src/main/java/org/matrix/android/sdk/api/auth/registration/RegistrationAvailability.kt
@@ -0,0 +1,24 @@
+/*
+ * Copyright 2020 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 {
+    data class Available(val available: Boolean): RegistrationAvailability()
+    data class NotAvailable(val failure: Failure.ServerError): RegistrationAvailability()
+}
\ No newline at end of file
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..7f25eedb23 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
@@ -87,3 +87,11 @@ fun Throwable.toRegistrationFlowResponse(): RegistrationFlowResponse? {
         null
     }
 }
+
+fun Throwable.isRegistrationAvailabilityError(): Boolean {
+    return this is Failure.ServerError
+            && (error.code == MatrixError.M_USER_IN_USE
+                    || error.code == MatrixError.M_INVALID_USERNAME
+                    || error.code == MatrixError.M_EXCLUSIVE)
+            && httpCode == 400
+}
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..6566aae5fe 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
@@ -16,6 +16,7 @@
 
 package org.matrix.android.sdk.internal.auth
 
+import org.matrix.android.sdk.api.auth.data.Availability
 import org.matrix.android.sdk.api.auth.data.Credentials
 import org.matrix.android.sdk.internal.auth.data.LoginFlowResponse
 import org.matrix.android.sdk.internal.auth.data.PasswordLoginParams
@@ -29,12 +30,8 @@ import org.matrix.android.sdk.internal.auth.registration.SuccessResult
 import org.matrix.android.sdk.internal.auth.registration.ValidationCodeBody
 import org.matrix.android.sdk.internal.auth.version.Versions
 import org.matrix.android.sdk.internal.network.NetworkConstants
-import retrofit2.http.Body
-import retrofit2.http.GET
-import retrofit2.http.Headers
-import retrofit2.http.POST
-import retrofit2.http.Path
-import retrofit2.http.Url
+import retrofit2.Call
+import retrofit2.http.*
 
 /**
  * The login REST API.
@@ -65,6 +62,12 @@ 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")
+    fun registerAvailable(@Query("username") username: String): Call<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/registration/DefaultRegistrationWizard.kt b/matrix-sdk-android/src/main/java/org/matrix/android/sdk/internal/auth/registration/DefaultRegistrationWizard.kt
index 91e414e689..3be95f6a4a 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
@@ -18,12 +18,10 @@ 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.RegistrationResult
-import org.matrix.android.sdk.api.auth.registration.RegistrationWizard
-import org.matrix.android.sdk.api.auth.registration.toFlowResult
+import org.matrix.android.sdk.api.auth.registration.*
 import org.matrix.android.sdk.api.failure.Failure
 import org.matrix.android.sdk.api.failure.Failure.RegistrationFlowError
+import org.matrix.android.sdk.api.failure.isRegistrationAvailabilityError
 import org.matrix.android.sdk.internal.auth.AuthAPI
 import org.matrix.android.sdk.internal.auth.PendingSessionStore
 import org.matrix.android.sdk.internal.auth.SessionCreator
@@ -41,6 +39,7 @@ internal class DefaultRegistrationWizard(
     private var pendingSessionData: PendingSessionData = pendingSessionStore.getPendingSessionData() ?: error("Pending session data should exist here")
 
     private val registerTask = DefaultRegisterTask(authAPI)
+    private val registerAvailableTask = RegisterAvailableTask(authAPI)
     private val registerAddThreePidTask = DefaultRegisterAddThreePidTask(authAPI)
     private val validateCodeTask = DefaultValidateCodeTask(authAPI)
 
@@ -203,4 +202,18 @@ internal class DefaultRegistrationWizard(
         val session = sessionCreator.createSession(credentials, pendingSessionData.homeServerConnectionConfig)
         return RegistrationResult.Success(session)
     }
+
+    override suspend fun registrationAvailable(userName: String): RegistrationAvailability {
+        val availability = try {
+            registerAvailableTask.execute(userName)
+        } catch (exception: Throwable) {
+            if(exception.isRegistrationAvailabilityError()) {
+                return RegistrationAvailability.NotAvailable(exception as Failure.ServerError)
+            } else {
+                throw exception
+            }
+        }
+
+        return RegistrationAvailability.Available(availability.available)
+    }
 }
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..aa2bb767f9
--- /dev/null
+++ b/matrix-sdk-android/src/main/java/org/matrix/android/sdk/internal/auth/registration/RegisterAvailableTask.kt
@@ -0,0 +1,30 @@
+/*
+ * Copyright 2020 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.data.Availability
+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 class RegisterAvailableTask(private val authAPI: AuthAPI) : Task<String, Availability> {
+    override suspend fun execute(params: String): Availability {
+        return executeRequest(null) {
+            apiCall = authAPI.registerAvailable(params)
+        }
+    }
+}
\ No newline at end of file