diff --git a/spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/mongo/PropertiesMongoConnectionDetails.java b/spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/mongo/PropertiesMongoConnectionDetails.java
index 4d6fb5c3d1f..74a91c9a1c8 100644
--- a/spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/mongo/PropertiesMongoConnectionDetails.java
+++ b/spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/mongo/PropertiesMongoConnectionDetails.java
@@ -16,6 +16,9 @@
 
 package org.springframework.boot.autoconfigure.mongo;
 
+import java.util.ArrayList;
+import java.util.List;
+
 import com.mongodb.ConnectionString;
 
 /**
@@ -24,6 +27,7 @@ import com.mongodb.ConnectionString;
  * @author Moritz Halbritter
  * @author Andy Wilkinson
  * @author Phillip Webb
+ * @author Scott Frederick
  * @since 3.1.0
  */
 public class PropertiesMongoConnectionDetails implements MongoConnectionDetails {
@@ -44,7 +48,9 @@ public class PropertiesMongoConnectionDetails implements MongoConnectionDetails
 		if (this.properties.getUsername() != null) {
 			builder.append(this.properties.getUsername());
 			builder.append(":");
-			builder.append(this.properties.getPassword());
+			if (this.properties.getPassword() != null) {
+				builder.append(this.properties.getPassword());
+			}
 			builder.append("@");
 		}
 		builder.append((this.properties.getHost() != null) ? this.properties.getHost() : "localhost");
@@ -55,20 +61,12 @@ public class PropertiesMongoConnectionDetails implements MongoConnectionDetails
 		if (this.properties.getAdditionalHosts() != null) {
 			builder.append(String.join(",", this.properties.getAdditionalHosts()));
 		}
-		if (this.properties.getMongoClientDatabase() != null || this.properties.getReplicaSetName() != null
-				|| this.properties.getAuthenticationDatabase() != null) {
-			builder.append("/");
-			if (this.properties.getMongoClientDatabase() != null) {
-				builder.append(this.properties.getMongoClientDatabase());
-			}
-			else if (this.properties.getAuthenticationDatabase() != null) {
-				builder.append(this.properties.getAuthenticationDatabase());
-			}
-			if (this.properties.getReplicaSetName() != null) {
-				builder.append("?");
-				builder.append("replicaSet=");
-				builder.append(this.properties.getReplicaSetName());
-			}
+		builder.append("/");
+		builder.append(this.properties.getMongoClientDatabase());
+		List<String> options = getOptions();
+		if (!options.isEmpty()) {
+			builder.append("?");
+			builder.append(String.join("&", options));
 		}
 		return new ConnectionString(builder.toString());
 	}
@@ -79,4 +77,15 @@ public class PropertiesMongoConnectionDetails implements MongoConnectionDetails
 				PropertiesMongoConnectionDetails.this.properties.getGridfs().getBucket());
 	}
 
+	private List<String> getOptions() {
+		List<String> options = new ArrayList<>();
+		if (this.properties.getReplicaSetName() != null) {
+			options.add("replicaSet=" + this.properties.getReplicaSetName());
+		}
+		if (this.properties.getUsername() != null && this.properties.getAuthenticationDatabase() != null) {
+			options.add("authSource=" + this.properties.getAuthenticationDatabase());
+		}
+		return options;
+	}
+
 }
diff --git a/spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/mongo/MongoAutoConfigurationTests.java b/spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/mongo/MongoAutoConfigurationTests.java
index 31947cb6824..342461ffc40 100644
--- a/spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/mongo/MongoAutoConfigurationTests.java
+++ b/spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/mongo/MongoAutoConfigurationTests.java
@@ -20,6 +20,7 @@ import java.util.concurrent.TimeUnit;
 
 import com.mongodb.ConnectionString;
 import com.mongodb.MongoClientSettings;
+import com.mongodb.MongoCredential;
 import com.mongodb.client.MongoClient;
 import com.mongodb.client.MongoClients;
 import com.mongodb.client.internal.MongoClientImpl;
@@ -107,6 +108,95 @@ class MongoAutoConfigurationTests {
 			});
 	}
 
+	@Test
+	void doesNotConfigureCredentialsWithoutUsername() {
+		this.contextRunner
+			.withPropertyValues("spring.data.mongodb.password=secret",
+					"spring.data.mongodb.authentication-database=authdb")
+			.run((context) -> assertThat(getSettings(context).getCredential()).isNull());
+	}
+
+	@Test
+	void configuresCredentialsFromPropertiesWithDefaultDatabase() {
+		this.contextRunner
+			.withPropertyValues("spring.data.mongodb.username=user", "spring.data.mongodb.password=secret")
+			.run((context) -> {
+				MongoCredential credential = getSettings(context).getCredential();
+				assertThat(credential.getUserName()).isEqualTo("user");
+				assertThat(credential.getPassword()).isEqualTo("secret".toCharArray());
+				assertThat(credential.getSource()).isEqualTo("test");
+			});
+	}
+
+	@Test
+	void configuresCredentialsFromPropertiesWithDatabase() {
+		this.contextRunner
+			.withPropertyValues("spring.data.mongodb.username=user", "spring.data.mongodb.password=secret",
+					"spring.data.mongodb.database=mydb")
+			.run((context) -> {
+				MongoCredential credential = getSettings(context).getCredential();
+				assertThat(credential.getUserName()).isEqualTo("user");
+				assertThat(credential.getPassword()).isEqualTo("secret".toCharArray());
+				assertThat(credential.getSource()).isEqualTo("mydb");
+			});
+	}
+
+	@Test
+	void configuresCredentialsFromPropertiesWithAuthDatabase() {
+		this.contextRunner
+			.withPropertyValues("spring.data.mongodb.username=user", "spring.data.mongodb.password=secret",
+					"spring.data.mongodb.database=mydb", "spring.data.mongodb.authentication-database=authdb")
+			.run((context) -> {
+				MongoCredential credential = getSettings(context).getCredential();
+				assertThat(credential.getUserName()).isEqualTo("user");
+				assertThat(credential.getPassword()).isEqualTo("secret".toCharArray());
+				assertThat(credential.getSource()).isEqualTo("authdb");
+			});
+	}
+
+	@Test
+	void doesNotConfigureCredentialsWithoutUsernameInUri() {
+		this.contextRunner.withPropertyValues("spring.data.mongodb.uri=mongodb://localhost/mydb?authSource=authdb")
+			.run((context) -> assertThat(getSettings(context).getCredential()).isNull());
+	}
+
+	@Test
+	void configuresCredentialsFromUriPropertyWithDefaultDatabase() {
+		this.contextRunner.withPropertyValues("spring.data.mongodb.uri=mongodb://user:secret@localhost/")
+			.run((context) -> {
+				MongoCredential credential = getSettings(context).getCredential();
+				assertThat(credential.getUserName()).isEqualTo("user");
+				assertThat(credential.getPassword()).isEqualTo("secret".toCharArray());
+				assertThat(credential.getSource()).isEqualTo("admin");
+			});
+	}
+
+	@Test
+	void configuresCredentialsFromUriPropertyWithDatabase() {
+		this.contextRunner
+			.withPropertyValues("spring.data.mongodb.uri=mongodb://user:secret@localhost/mydb",
+					"spring.data.mongodb.database=notused", "spring.data.mongodb.authentication-database=notused")
+			.run((context) -> {
+				MongoCredential credential = getSettings(context).getCredential();
+				assertThat(credential.getUserName()).isEqualTo("user");
+				assertThat(credential.getPassword()).isEqualTo("secret".toCharArray());
+				assertThat(credential.getSource()).isEqualTo("mydb");
+			});
+	}
+
+	@Test
+	void configuresCredentialsFromUriPropertyWithAuthDatabase() {
+		this.contextRunner
+			.withPropertyValues("spring.data.mongodb.uri=mongodb://user:secret@localhost/mydb?authSource=authdb",
+					"spring.data.mongodb.database=notused", "spring.data.mongodb.authentication-database=notused")
+			.run((context) -> {
+				MongoCredential credential = getSettings(context).getCredential();
+				assertThat(credential.getUserName()).isEqualTo("user");
+				assertThat(credential.getPassword()).isEqualTo("secret".toCharArray());
+				assertThat(credential.getSource()).isEqualTo("authdb");
+			});
+	}
+
 	@Test
 	void configuresSingleClient() {
 		this.contextRunner.withUserConfiguration(FallbackMongoClientConfig.class)
diff --git a/spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/mongo/MongoReactiveAutoConfigurationTests.java b/spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/mongo/MongoReactiveAutoConfigurationTests.java
index 44e311be1d7..7f3fe1ef0b1 100644
--- a/spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/mongo/MongoReactiveAutoConfigurationTests.java
+++ b/spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/mongo/MongoReactiveAutoConfigurationTests.java
@@ -21,6 +21,7 @@ import java.util.concurrent.atomic.AtomicReference;
 
 import com.mongodb.ConnectionString;
 import com.mongodb.MongoClientSettings;
+import com.mongodb.MongoCredential;
 import com.mongodb.ReadPreference;
 import com.mongodb.connection.AsynchronousSocketChannelStreamFactoryFactory;
 import com.mongodb.connection.SslSettings;
@@ -121,6 +122,95 @@ class MongoReactiveAutoConfigurationTests {
 			});
 	}
 
+	@Test
+	void doesNotConfigureCredentialsWithoutUsername() {
+		this.contextRunner
+			.withPropertyValues("spring.data.mongodb.password=secret",
+					"spring.data.mongodb.authentication-database=authdb")
+			.run((context) -> assertThat(getSettings(context).getCredential()).isNull());
+	}
+
+	@Test
+	void configuresCredentialsFromPropertiesWithDefaultDatabase() {
+		this.contextRunner
+			.withPropertyValues("spring.data.mongodb.username=user", "spring.data.mongodb.password=secret")
+			.run((context) -> {
+				MongoCredential credential = getSettings(context).getCredential();
+				assertThat(credential.getUserName()).isEqualTo("user");
+				assertThat(credential.getPassword()).isEqualTo("secret".toCharArray());
+				assertThat(credential.getSource()).isEqualTo("test");
+			});
+	}
+
+	@Test
+	void configuresCredentialsFromPropertiesWithDatabase() {
+		this.contextRunner
+			.withPropertyValues("spring.data.mongodb.username=user", "spring.data.mongodb.password=secret",
+					"spring.data.mongodb.database=mydb")
+			.run((context) -> {
+				MongoCredential credential = getSettings(context).getCredential();
+				assertThat(credential.getUserName()).isEqualTo("user");
+				assertThat(credential.getPassword()).isEqualTo("secret".toCharArray());
+				assertThat(credential.getSource()).isEqualTo("mydb");
+			});
+	}
+
+	@Test
+	void configuresCredentialsFromPropertiesWithAuthDatabase() {
+		this.contextRunner
+			.withPropertyValues("spring.data.mongodb.username=user", "spring.data.mongodb.password=secret",
+					"spring.data.mongodb.database=mydb", "spring.data.mongodb.authentication-database=authdb")
+			.run((context) -> {
+				MongoCredential credential = getSettings(context).getCredential();
+				assertThat(credential.getUserName()).isEqualTo("user");
+				assertThat(credential.getPassword()).isEqualTo("secret".toCharArray());
+				assertThat(credential.getSource()).isEqualTo("authdb");
+			});
+	}
+
+	@Test
+	void doesNotConfigureCredentialsWithoutUsernameInUri() {
+		this.contextRunner.withPropertyValues("spring.data.mongodb.uri=mongodb://localhost/mydb?authSource=authdb")
+			.run((context) -> assertThat(getSettings(context).getCredential()).isNull());
+	}
+
+	@Test
+	void configuresCredentialsFromUriPropertyWithDefaultDatabase() {
+		this.contextRunner.withPropertyValues("spring.data.mongodb.uri=mongodb://user:secret@localhost/")
+			.run((context) -> {
+				MongoCredential credential = getSettings(context).getCredential();
+				assertThat(credential.getUserName()).isEqualTo("user");
+				assertThat(credential.getPassword()).isEqualTo("secret".toCharArray());
+				assertThat(credential.getSource()).isEqualTo("admin");
+			});
+	}
+
+	@Test
+	void configuresCredentialsFromUriPropertyWithDatabase() {
+		this.contextRunner
+			.withPropertyValues("spring.data.mongodb.uri=mongodb://user:secret@localhost/mydb",
+					"spring.data.mongodb.database=notused", "spring.data.mongodb.authentication-database=notused")
+			.run((context) -> {
+				MongoCredential credential = getSettings(context).getCredential();
+				assertThat(credential.getUserName()).isEqualTo("user");
+				assertThat(credential.getPassword()).isEqualTo("secret".toCharArray());
+				assertThat(credential.getSource()).isEqualTo("mydb");
+			});
+	}
+
+	@Test
+	void configuresCredentialsFromUriPropertyWithAuthDatabase() {
+		this.contextRunner
+			.withPropertyValues("spring.data.mongodb.uri=mongodb://user:secret@localhost/mydb?authSource=authdb",
+					"spring.data.mongodb.database=notused", "spring.data.mongodb.authentication-database=notused")
+			.run((context) -> {
+				MongoCredential credential = getSettings(context).getCredential();
+				assertThat(credential.getUserName()).isEqualTo("user");
+				assertThat(credential.getPassword()).isEqualTo("secret".toCharArray());
+				assertThat(credential.getSource()).isEqualTo("authdb");
+			});
+	}
+
 	@Test
 	void nettyStreamFactoryFactoryIsConfiguredAutomatically() {
 		AtomicReference<EventLoopGroup> eventLoopGroupReference = new AtomicReference<>();
diff --git a/spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/mongo/PropertiesMongoConnectionDetailsTests.java b/spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/mongo/PropertiesMongoConnectionDetailsTests.java
index 2f9887f468d..1a1372f4576 100644
--- a/spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/mongo/PropertiesMongoConnectionDetailsTests.java
+++ b/spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/mongo/PropertiesMongoConnectionDetailsTests.java
@@ -25,11 +25,66 @@ import static org.assertj.core.api.Assertions.assertThat;
  * Tests for {@link PropertiesMongoConnectionDetails}.
  *
  * @author Christoph Dreis
+ * @author Scott Frederick
  */
 class PropertiesMongoConnectionDetailsTests {
 
 	private final MongoProperties properties = new MongoProperties();
 
+	@Test
+	void credentialsCanBeConfiguredWithUsername() {
+		this.properties.setUsername("user");
+		ConnectionString connectionString = getConnectionString();
+		assertThat(connectionString.getUsername()).isEqualTo("user");
+		assertThat(connectionString.getPassword()).isEmpty();
+		assertThat(connectionString.getCredential().getUserName()).isEqualTo("user");
+		assertThat(connectionString.getCredential().getPassword()).isEmpty();
+		assertThat(connectionString.getCredential().getSource()).isEqualTo("test");
+	}
+
+	@Test
+	void credentialsCanBeConfiguredWithUsernameAndPassword() {
+		this.properties.setUsername("user");
+		this.properties.setPassword("secret".toCharArray());
+		ConnectionString connectionString = getConnectionString();
+		assertThat(connectionString.getUsername()).isEqualTo("user");
+		assertThat(connectionString.getPassword()).isEqualTo("secret".toCharArray());
+		assertThat(connectionString.getCredential().getUserName()).isEqualTo("user");
+		assertThat(connectionString.getCredential().getPassword()).isEqualTo("secret".toCharArray());
+		assertThat(connectionString.getCredential().getSource()).isEqualTo("test");
+	}
+
+	@Test
+	void databaseCanBeConfigured() {
+		this.properties.setDatabase("db");
+		ConnectionString connectionString = getConnectionString();
+		assertThat(connectionString.getDatabase()).isEqualTo("db");
+	}
+
+	@Test
+	void databaseHasDefaultWhenNotConfigured() {
+		ConnectionString connectionString = getConnectionString();
+		assertThat(connectionString.getDatabase()).isEqualTo("test");
+	}
+
+	@Test
+	void authenticationDatabaseCanBeConfigured() {
+		this.properties.setUsername("user");
+		this.properties.setDatabase("db");
+		this.properties.setAuthenticationDatabase("authdb");
+		ConnectionString connectionString = getConnectionString();
+		assertThat(connectionString.getDatabase()).isEqualTo("db");
+		assertThat(connectionString.getCredential().getSource()).isEqualTo("authdb");
+		assertThat(connectionString.getCredential().getUserName()).isEqualTo("user");
+	}
+
+	@Test
+	void authenticationDatabaseIsNotConfiguredWhenUsernameIsNotConfigured() {
+		this.properties.setAuthenticationDatabase("authdb");
+		ConnectionString connectionString = getConnectionString();
+		assertThat(connectionString.getCredential()).isNull();
+	}
+
 	@Test
 	void replicaSetCanBeConfigured() {
 		this.properties.setReplicaSetName("test");
@@ -37,6 +92,16 @@ class PropertiesMongoConnectionDetailsTests {
 		assertThat(connectionString.getRequiredReplicaSetName()).isEqualTo("test");
 	}
 
+	@Test
+	void replicaSetCanBeConfiguredWithDatabase() {
+		this.properties.setUsername("user");
+		this.properties.setDatabase("db");
+		this.properties.setReplicaSetName("test");
+		ConnectionString connectionString = getConnectionString();
+		assertThat(connectionString.getDatabase()).isEqualTo("db");
+		assertThat(connectionString.getRequiredReplicaSetName()).isEqualTo("test");
+	}
+
 	private PropertiesMongoConnectionDetails createConnectionDetails() {
 		return new PropertiesMongoConnectionDetails(this.properties);
 	}