diff --git a/service/src/main/java/org/whispersystems/textsecuregcm/WhisperServerService.java b/service/src/main/java/org/whispersystems/textsecuregcm/WhisperServerService.java
index 7bbdc71ee..7a1bdbf57 100644
--- a/service/src/main/java/org/whispersystems/textsecuregcm/WhisperServerService.java
+++ b/service/src/main/java/org/whispersystems/textsecuregcm/WhisperServerService.java
@@ -157,13 +157,14 @@ public class WhisperServerService extends Application<WhisperServerConfiguration
     FaultTolerantDatabase messageDatabase = new FaultTolerantDatabase("message_database", messageJdbi, config.getMessageStoreConfiguration().getCircuitBreakerConfiguration());
     FaultTolerantDatabase abuseDatabase   = new FaultTolerantDatabase("abuse_database", abuseJdbi, config.getAbuseDatabaseConfiguration().getCircuitBreakerConfiguration());
 
-    Accounts         accounts         = new Accounts(accountDatabase);
-    PendingAccounts  pendingAccounts  = new PendingAccounts(accountDatabase);
-    PendingDevices   pendingDevices   = new PendingDevices(accountDatabase);
-    Usernames        usernames        = new Usernames(accountDatabase);
-    Keys             keys             = new Keys(keysDatabase);
-    Messages         messages         = new Messages(messageDatabase);
-    AbusiveHostRules abusiveHostRules = new AbusiveHostRules(abuseDatabase);
+    Accounts          accounts          = new Accounts(accountDatabase);
+    PendingAccounts   pendingAccounts   = new PendingAccounts(accountDatabase);
+    PendingDevices    pendingDevices    = new PendingDevices (accountDatabase);
+    Usernames         usernames         = new Usernames(accountDatabase);
+    ReservedUsernames reservedUsernames = new ReservedUsernames(accountDatabase);
+    Keys              keys              = new Keys(keysDatabase);
+    Messages          messages          = new Messages(messageDatabase);
+    AbusiveHostRules  abusiveHostRules  = new AbusiveHostRules(abuseDatabase);
 
     RedisClientFactory cacheClientFactory         = new RedisClientFactory("main_cache", config.getCacheConfiguration().getUrl(), config.getCacheConfiguration().getReplicaUrls(), config.getCacheConfiguration().getCircuitBreakerConfiguration());
     RedisClientFactory directoryClientFactory     = new RedisClientFactory("directory_cache", config.getDirectoryConfiguration().getRedisConfiguration().getUrl(), config.getDirectoryConfiguration().getRedisConfiguration().getReplicaUrls(), config.getDirectoryConfiguration().getRedisConfiguration().getCircuitBreakerConfiguration());
@@ -180,7 +181,7 @@ public class WhisperServerService extends Application<WhisperServerConfiguration
     PendingAccountsManager     pendingAccountsManager     = new PendingAccountsManager(pendingAccounts, cacheClient);
     PendingDevicesManager      pendingDevicesManager      = new PendingDevicesManager (pendingDevices, cacheClient );
     AccountsManager            accountsManager            = new AccountsManager(accounts, directory, cacheClient);
-    UsernamesManager           usernamesManager           = new UsernamesManager(usernames, cacheClient);
+    UsernamesManager           usernamesManager           = new UsernamesManager(usernames, reservedUsernames, cacheClient);
     MessagesCache              messagesCache              = new MessagesCache(messagesClient, messages, accountsManager, config.getMessageCacheConfiguration().getPersistDelayMinutes());
     MessagesManager            messagesManager            = new MessagesManager(messages, messagesCache);
     DeadLetterHandler          deadLetterHandler          = new DeadLetterHandler(messagesManager);
diff --git a/service/src/main/java/org/whispersystems/textsecuregcm/storage/ReservedUsernames.java b/service/src/main/java/org/whispersystems/textsecuregcm/storage/ReservedUsernames.java
new file mode 100644
index 000000000..0b93af255
--- /dev/null
+++ b/service/src/main/java/org/whispersystems/textsecuregcm/storage/ReservedUsernames.java
@@ -0,0 +1,53 @@
+package org.whispersystems.textsecuregcm.storage;
+
+import com.codahale.metrics.MetricRegistry;
+import com.codahale.metrics.SharedMetricRegistries;
+import com.codahale.metrics.Timer;
+import com.google.common.annotations.VisibleForTesting;
+import org.whispersystems.textsecuregcm.util.Constants;
+
+import java.util.Optional;
+import java.util.UUID;
+
+import static com.codahale.metrics.MetricRegistry.name;
+
+public class ReservedUsernames {
+
+  public static final String ID       = "id";
+  public static final String UID      = "uuid";
+  public static final String USERNAME = "username";
+
+  private final MetricRegistry metricRegistry = SharedMetricRegistries.getOrCreate(Constants.METRICS_NAME);
+  private final Timer          queryTimer     = metricRegistry.timer(name(ReservedUsernames.class, "query"));
+
+  private final FaultTolerantDatabase database;
+
+  public ReservedUsernames(FaultTolerantDatabase database) {
+    this.database = database;
+  }
+
+  public boolean isReserved(String username, UUID uuid) {
+    return database.with(jdbi -> jdbi.withHandle(handle -> {
+      try (Timer.Context ignored = queryTimer.time()) {
+        Optional<Integer> reservations = handle.createQuery("SELECT COUNT(*) FROM reserved_usernames WHERE " + UID + " != :uuid AND :username ~* " + USERNAME)
+                                               .bind("username", username)
+                                               .bind("uuid", uuid)
+                                               .mapTo(Integer.class)
+                                               .findFirst();
+
+        return reservations.isPresent() && reservations.get() > 0;
+      }
+    }));
+  }
+
+  @VisibleForTesting
+  public void setReserved(String username, UUID reservedFor) {
+    database.use(jdbi -> jdbi.useHandle(handle -> {
+      handle.createUpdate("INSERT INTO reserved_usernames (" + USERNAME + ", " + UID + ") VALUES(:username, :uuid)")
+            .bind("username", username)
+            .bind("uuid", reservedFor)
+            .execute();
+    }));
+  }
+
+}
diff --git a/service/src/main/java/org/whispersystems/textsecuregcm/storage/UsernamesManager.java b/service/src/main/java/org/whispersystems/textsecuregcm/storage/UsernamesManager.java
index 5816affba..09bb3ee63 100644
--- a/service/src/main/java/org/whispersystems/textsecuregcm/storage/UsernamesManager.java
+++ b/service/src/main/java/org/whispersystems/textsecuregcm/storage/UsernamesManager.java
@@ -30,15 +30,21 @@ public class UsernamesManager {
   private final Logger logger = LoggerFactory.getLogger(AccountsManager.class);
 
   private final Usernames           usernames;
+  private final ReservedUsernames   reservedUsernames;
   private final ReplicatedJedisPool cacheClient;
 
-  public UsernamesManager(Usernames usernames, ReplicatedJedisPool cacheClient) {
-    this.usernames   = usernames;
-    this.cacheClient = cacheClient;
+  public UsernamesManager(Usernames usernames, ReservedUsernames reservedUsernames, ReplicatedJedisPool cacheClient) {
+    this.usernames         = usernames;
+    this.reservedUsernames = reservedUsernames;
+    this.cacheClient       = cacheClient;
   }
 
   public boolean put(UUID uuid, String username) {
     try (Timer.Context ignored = createTimer.time()) {
+      if (reservedUsernames.isReserved(username, uuid)) {
+        return false;
+      }
+
       if (databasePut(uuid, username)) {
         redisSet(uuid, username);
 
diff --git a/service/src/main/resources/accountsdb.xml b/service/src/main/resources/accountsdb.xml
index 17758cb82..4ff07f2c2 100644
--- a/service/src/main/resources/accountsdb.xml
+++ b/service/src/main/resources/accountsdb.xml
@@ -223,4 +223,20 @@
         </createTable>
     </changeSet>
 
+    <changeSet id="10" author="moxie">
+        <createTable tableName="reserved_usernames">
+            <column name="id" type="bigint" autoIncrement="true">
+                <constraints nullable="false" primaryKey="true"/>
+            </column>
+
+            <column name="username" type="text">
+                <constraints nullable="false" unique="true"/>
+            </column>
+
+            <column name="uuid" type="uuid">
+                <constraints nullable="false"/>
+            </column>
+        </createTable>
+    </changeSet>
+
 </databaseChangeLog>
diff --git a/service/src/test/java/org/whispersystems/textsecuregcm/tests/storage/ReservedUsernamesTest.java b/service/src/test/java/org/whispersystems/textsecuregcm/tests/storage/ReservedUsernamesTest.java
new file mode 100644
index 000000000..975a4284d
--- /dev/null
+++ b/service/src/test/java/org/whispersystems/textsecuregcm/tests/storage/ReservedUsernamesTest.java
@@ -0,0 +1,71 @@
+package org.whispersystems.textsecuregcm.tests.storage;
+
+import com.opentable.db.postgres.embedded.LiquibasePreparer;
+import com.opentable.db.postgres.junit.EmbeddedPostgresRules;
+import com.opentable.db.postgres.junit.PreparedDbRule;
+import org.jdbi.v3.core.Jdbi;
+import org.junit.Before;
+import org.junit.Rule;
+import org.junit.Test;
+import org.whispersystems.textsecuregcm.configuration.CircuitBreakerConfiguration;
+import org.whispersystems.textsecuregcm.storage.FaultTolerantDatabase;
+import org.whispersystems.textsecuregcm.storage.ReservedUsernames;
+import org.whispersystems.textsecuregcm.storage.Usernames;
+
+import java.io.IOException;
+import java.sql.PreparedStatement;
+import java.sql.ResultSet;
+import java.sql.SQLException;
+import java.util.Optional;
+import java.util.UUID;
+
+import static junit.framework.TestCase.assertTrue;
+import static org.assertj.core.api.AssertionsForClassTypes.assertThat;
+import static org.junit.Assert.assertFalse;
+
+public class ReservedUsernamesTest {
+
+  @Rule
+  public PreparedDbRule db = EmbeddedPostgresRules.preparedDatabase(LiquibasePreparer.forClasspathLocation("accountsdb.xml"));
+
+  private ReservedUsernames reserved;
+
+  @Before
+  public void setupAccountsDao() {
+    FaultTolerantDatabase faultTolerantDatabase = new FaultTolerantDatabase("reservedUsernamesTest",
+                                                                            Jdbi.create(db.getTestDatabase()),
+                                                                            new CircuitBreakerConfiguration());
+
+    this.reserved = new ReservedUsernames(faultTolerantDatabase);
+  }
+
+  @Test
+  public void testReservedRegexp() {
+    UUID   reservedFor = UUID.randomUUID();
+    String username    = ".*myusername.*";
+
+    reserved.setReserved(username, reservedFor);
+
+
+    assertTrue(reserved.isReserved("myusername", UUID.randomUUID()));
+    assertFalse(reserved.isReserved("myusername", reservedFor));
+    assertFalse(reserved.isReserved("thyusername", UUID.randomUUID()));
+    assertTrue(reserved.isReserved("somemyusername", UUID.randomUUID()));
+    assertTrue(reserved.isReserved("myusernamesome", UUID.randomUUID()));
+    assertTrue(reserved.isReserved("somemyusernamesome", UUID.randomUUID()));
+  }
+
+  @Test
+  public void testReservedLiteral() {
+    UUID   reservedFor = UUID.randomUUID();
+    String username    = "^foobar$";
+
+    reserved.setReserved(username, reservedFor);
+
+    assertTrue(reserved.isReserved("foobar", UUID.randomUUID()));
+    assertFalse(reserved.isReserved("foobar", reservedFor));
+    assertFalse(reserved.isReserved("somefoobar", UUID.randomUUID()));
+    assertFalse(reserved.isReserved("foobarsome", UUID.randomUUID()));
+    assertFalse(reserved.isReserved("somefoobarsome", UUID.randomUUID()));
+  }
+}
diff --git a/service/src/test/java/org/whispersystems/textsecuregcm/tests/storage/UsernamesManagerTest.java b/service/src/test/java/org/whispersystems/textsecuregcm/tests/storage/UsernamesManagerTest.java
index 8f8791890..3afda4ec3 100644
--- a/service/src/test/java/org/whispersystems/textsecuregcm/tests/storage/UsernamesManagerTest.java
+++ b/service/src/test/java/org/whispersystems/textsecuregcm/tests/storage/UsernamesManagerTest.java
@@ -2,21 +2,16 @@ package org.whispersystems.textsecuregcm.tests.storage;
 
 import org.junit.Test;
 import org.whispersystems.textsecuregcm.redis.ReplicatedJedisPool;
-import org.whispersystems.textsecuregcm.storage.Account;
-import org.whispersystems.textsecuregcm.storage.Accounts;
-import org.whispersystems.textsecuregcm.storage.AccountsManager;
-import org.whispersystems.textsecuregcm.storage.DirectoryManager;
+import org.whispersystems.textsecuregcm.storage.ReservedUsernames;
 import org.whispersystems.textsecuregcm.storage.Usernames;
 import org.whispersystems.textsecuregcm.storage.UsernamesManager;
 
-import java.util.HashSet;
 import java.util.Optional;
 import java.util.UUID;
 
 import static junit.framework.TestCase.assertSame;
 import static junit.framework.TestCase.assertTrue;
 import static org.junit.Assert.assertEquals;
-import static org.mockito.ArgumentMatchers.anyString;
 import static org.mockito.ArgumentMatchers.eq;
 import static org.mockito.Mockito.*;
 import redis.clients.jedis.Jedis;
@@ -29,13 +24,14 @@ public class UsernamesManagerTest {
     ReplicatedJedisPool cacheClient = mock(ReplicatedJedisPool.class);
     Jedis               jedis       = mock(Jedis.class              );
     Usernames           usernames   = mock(Usernames.class          );
+    ReservedUsernames   reserved    = mock(ReservedUsernames.class);
 
     UUID uuid = UUID.randomUUID();
 
     when(cacheClient.getReadResource()).thenReturn(jedis);
     when(jedis.get(eq("UsernameByUsername::n00bkiller"))).thenReturn(uuid.toString());
 
-    UsernamesManager usernamesManager = new UsernamesManager(usernames, cacheClient);
+    UsernamesManager usernamesManager = new UsernamesManager(usernames, reserved, cacheClient);
     Optional<UUID>   retrieved        = usernamesManager.get("n00bkiller");
 
     assertTrue(retrieved.isPresent());
@@ -52,13 +48,14 @@ public class UsernamesManagerTest {
     ReplicatedJedisPool cacheClient = mock(ReplicatedJedisPool.class);
     Jedis               jedis       = mock(Jedis.class              );
     Usernames           usernames   = mock(Usernames.class          );
+    ReservedUsernames   reserved    = mock(ReservedUsernames.class);
 
     UUID uuid = UUID.randomUUID();
 
     when(cacheClient.getReadResource()).thenReturn(jedis);
     when(jedis.get(eq("UsernameByUuid::" + uuid.toString()))).thenReturn("n00bkiller");
 
-    UsernamesManager usernamesManager = new UsernamesManager(usernames, cacheClient);
+    UsernamesManager usernamesManager = new UsernamesManager(usernames, reserved, cacheClient);
     Optional<String> retrieved        = usernamesManager.get(uuid);
 
     assertTrue(retrieved.isPresent());
@@ -76,6 +73,7 @@ public class UsernamesManagerTest {
     ReplicatedJedisPool cacheClient = mock(ReplicatedJedisPool.class);
     Jedis               jedis       = mock(Jedis.class              );
     Usernames           usernames   = mock(Usernames.class          );
+    ReservedUsernames   reserved    = mock(ReservedUsernames.class);
 
     UUID                uuid             = UUID.randomUUID();
 
@@ -85,7 +83,7 @@ public class UsernamesManagerTest {
     when(jedis.get(eq("UsernameByUsername::n00bkiller"))).thenReturn(null);
     when(usernames.get(eq("n00bkiller"))).thenReturn(Optional.of(uuid));
 
-    UsernamesManager usernamesManager = new UsernamesManager(usernames, cacheClient);
+    UsernamesManager usernamesManager = new UsernamesManager(usernames, reserved, cacheClient);
     Optional<UUID>   retrieved        = usernamesManager.get("n00bkiller");
 
     assertTrue(retrieved.isPresent());
@@ -106,6 +104,7 @@ public class UsernamesManagerTest {
     ReplicatedJedisPool cacheClient = mock(ReplicatedJedisPool.class);
     Jedis               jedis       = mock(Jedis.class              );
     Usernames           usernames   = mock(Usernames.class          );
+    ReservedUsernames   reserved    = mock(ReservedUsernames.class);
 
     UUID uuid = UUID.randomUUID();
 
@@ -114,7 +113,7 @@ public class UsernamesManagerTest {
     when(jedis.get(eq("UsernameByUuid::" + uuid.toString()))).thenReturn(null);
     when(usernames.get(eq(uuid))).thenReturn(Optional.of("n00bkiller"));
 
-    UsernamesManager usernamesManager = new UsernamesManager(usernames, cacheClient);
+    UsernamesManager usernamesManager = new UsernamesManager(usernames, reserved, cacheClient);
     Optional<String> retrieved        = usernamesManager.get(uuid);
 
     assertTrue(retrieved.isPresent());
@@ -135,6 +134,7 @@ public class UsernamesManagerTest {
     ReplicatedJedisPool cacheClient = mock(ReplicatedJedisPool.class);
     Jedis               jedis       = mock(Jedis.class              );
     Usernames           usernames   = mock(Usernames.class          );
+    ReservedUsernames   reserved    = mock(ReservedUsernames.class);
 
     UUID                uuid        = UUID.randomUUID();
 
@@ -143,7 +143,7 @@ public class UsernamesManagerTest {
     when(jedis.get(eq("UsernameByUsername::n00bkiller"))).thenThrow(new JedisException("Connection lost!"));
     when(usernames.get(eq("n00bkiller"))).thenReturn(Optional.of(uuid));
 
-    UsernamesManager usernamesManager = new UsernamesManager(usernames, cacheClient);
+    UsernamesManager usernamesManager = new UsernamesManager(usernames, reserved, cacheClient);
     Optional<UUID>   retrieved        = usernamesManager.get("n00bkiller");
 
     assertTrue(retrieved.isPresent());
@@ -164,6 +164,7 @@ public class UsernamesManagerTest {
     ReplicatedJedisPool cacheClient = mock(ReplicatedJedisPool.class);
     Jedis               jedis       = mock(Jedis.class              );
     Usernames           usernames   = mock(Usernames.class          );
+    ReservedUsernames   reserved    = mock(ReservedUsernames.class);
 
     UUID                uuid        = UUID.randomUUID();
 
@@ -172,7 +173,7 @@ public class UsernamesManagerTest {
     when(jedis.get(eq("UsernameByUuid::" + uuid))).thenThrow(new JedisException("Connection lost!"));
     when(usernames.get(eq(uuid))).thenReturn(Optional.of("n00bkiller"));
 
-    UsernamesManager usernamesManager = new UsernamesManager(usernames, cacheClient);
+    UsernamesManager usernamesManager = new UsernamesManager(usernames, reserved, cacheClient);
     Optional<String>   retrieved        = usernamesManager.get(uuid);
 
     assertTrue(retrieved.isPresent());