diff --git a/hadoop-common-project/hadoop-common/CHANGES.txt b/hadoop-common-project/hadoop-common/CHANGES.txt
index b2c1af3e31..d9e6180bc1 100644
--- a/hadoop-common-project/hadoop-common/CHANGES.txt
+++ b/hadoop-common-project/hadoop-common/CHANGES.txt
@@ -488,6 +488,9 @@ Release 2.7.0 - UNRELEASED
 
     HADOOP-11261 Set custom endpoint for S3A. (Thomas Demoor via stevel)
 
+    HADOOP-11171 Enable using a proxy server to connect to S3a.
+    (Thomas Demoor via stevel)
+
   OPTIMIZATIONS
 
     HADOOP-11323. WritableComparator#compare keeps reference to byte array.
diff --git a/hadoop-tools/hadoop-aws/src/main/java/org/apache/hadoop/fs/s3a/Constants.java b/hadoop-tools/hadoop-aws/src/main/java/org/apache/hadoop/fs/s3a/Constants.java
index 0232961469..b6863bb162 100644
--- a/hadoop-tools/hadoop-aws/src/main/java/org/apache/hadoop/fs/s3a/Constants.java
+++ b/hadoop-tools/hadoop-aws/src/main/java/org/apache/hadoop/fs/s3a/Constants.java
@@ -31,6 +31,13 @@ public class Constants {
 
   //use a custom endpoint?
   public static final String ENDPOINT = "fs.s3a.endpoint";
+  //connect to s3 through a proxy server?
+  public static final String PROXY_HOST = "fs.s3a.proxy.host";
+  public static final String PROXY_PORT = "fs.s3a.proxy.port";
+  public static final String PROXY_USERNAME = "fs.s3a.proxy.username";
+  public static final String PROXY_PASSWORD = "fs.s3a.proxy.password";
+  public static final String PROXY_DOMAIN = "fs.s3a.proxy.domain";
+  public static final String PROXY_WORKSTATION = "fs.s3a.proxy.workstation";
 
   // number of times we should retry errors
   public static final String MAX_ERROR_RETRIES = "fs.s3a.attempts.maximum";
diff --git a/hadoop-tools/hadoop-aws/src/main/java/org/apache/hadoop/fs/s3a/S3AFileSystem.java b/hadoop-tools/hadoop-aws/src/main/java/org/apache/hadoop/fs/s3a/S3AFileSystem.java
index d8cf73f8f8..0e4d54f132 100644
--- a/hadoop-tools/hadoop-aws/src/main/java/org/apache/hadoop/fs/s3a/S3AFileSystem.java
+++ b/hadoop-tools/hadoop-aws/src/main/java/org/apache/hadoop/fs/s3a/S3AFileSystem.java
@@ -169,13 +169,54 @@ public void initialize(URI name, Configuration conf) throws IOException {
     ClientConfiguration awsConf = new ClientConfiguration();
     awsConf.setMaxConnections(conf.getInt(MAXIMUM_CONNECTIONS, 
       DEFAULT_MAXIMUM_CONNECTIONS));
-    awsConf.setProtocol(conf.getBoolean(SECURE_CONNECTIONS, 
-      DEFAULT_SECURE_CONNECTIONS) ?  Protocol.HTTPS : Protocol.HTTP);
+    boolean secureConnections = conf.getBoolean(SECURE_CONNECTIONS,
+        DEFAULT_SECURE_CONNECTIONS);
+    awsConf.setProtocol(secureConnections ?  Protocol.HTTPS : Protocol.HTTP);
     awsConf.setMaxErrorRetry(conf.getInt(MAX_ERROR_RETRIES, 
       DEFAULT_MAX_ERROR_RETRIES));
     awsConf.setSocketTimeout(conf.getInt(SOCKET_TIMEOUT, 
       DEFAULT_SOCKET_TIMEOUT));
 
+    String proxyHost = conf.getTrimmed(PROXY_HOST,"");
+    int proxyPort = conf.getInt(PROXY_PORT, -1);
+    if (!proxyHost.isEmpty()) {
+      awsConf.setProxyHost(proxyHost);
+      if (proxyPort >= 0) {
+        awsConf.setProxyPort(proxyPort);
+      } else {
+        if (secureConnections) {
+          LOG.warn("Proxy host set without port. Using HTTPS default 443");
+          awsConf.setProxyPort(443);
+        } else {
+          LOG.warn("Proxy host set without port. Using HTTP default 80");
+          awsConf.setProxyPort(80);
+        }
+      }
+      String proxyUsername = conf.getTrimmed(PROXY_USERNAME);
+      String proxyPassword = conf.getTrimmed(PROXY_PASSWORD);
+      if ((proxyUsername == null) != (proxyPassword == null)) {
+        String msg = "Proxy error: " + PROXY_USERNAME + " or " +
+            PROXY_PASSWORD + " set without the other.";
+        LOG.error(msg);
+        throw new IllegalArgumentException(msg);
+      }
+      awsConf.setProxyUsername(proxyUsername);
+      awsConf.setProxyPassword(proxyPassword);
+      awsConf.setProxyDomain(conf.getTrimmed(PROXY_DOMAIN));
+      awsConf.setProxyWorkstation(conf.getTrimmed(PROXY_WORKSTATION));
+      if (LOG.isDebugEnabled()) {
+        LOG.debug("Using proxy server {}:{} as user {} with password {} on " +
+                "domain {} as workstation {}", awsConf.getProxyHost(),
+            awsConf.getProxyPort(), String.valueOf(awsConf.getProxyUsername()),
+            awsConf.getProxyPassword(), awsConf.getProxyDomain(),
+            awsConf.getProxyWorkstation());
+      }
+    } else if (proxyPort >= 0) {
+      String msg = "Proxy error: " + PROXY_PORT + " set without " + PROXY_HOST;
+      LOG.error(msg);
+      throw new IllegalArgumentException(msg);
+    }
+
     s3 = new AmazonS3Client(credentials, awsConf);
     String endPoint = conf.getTrimmed(ENDPOINT,"");
     if (!endPoint.isEmpty()) {
diff --git a/hadoop-tools/hadoop-aws/src/test/java/org/apache/hadoop/fs/s3a/TestS3AConfiguration.java b/hadoop-tools/hadoop-aws/src/test/java/org/apache/hadoop/fs/s3a/TestS3AConfiguration.java
index e4a14d0f0b..25068f8d9a 100644
--- a/hadoop-tools/hadoop-aws/src/test/java/org/apache/hadoop/fs/s3a/TestS3AConfiguration.java
+++ b/hadoop-tools/hadoop-aws/src/test/java/org/apache/hadoop/fs/s3a/TestS3AConfiguration.java
@@ -20,6 +20,7 @@
 
 import com.amazonaws.services.s3.AmazonS3Client;
 import org.apache.commons.lang.StringUtils;
+import com.amazonaws.AmazonClientException;
 import org.apache.hadoop.conf.Configuration;
 
 import org.junit.Rule;
@@ -82,4 +83,98 @@ public void TestEndpoint() throws Exception {
           endPointRegion, s3.getBucketLocation(fs.getUri().getHost()));
     }
   }
+
+  @Test
+  public void TestProxyConnection() throws Exception {
+    conf = new Configuration();
+    conf.setInt(Constants.MAX_ERROR_RETRIES, 2);
+    conf.set(Constants.PROXY_HOST, "127.0.0.1");
+    conf.setInt(Constants.PROXY_PORT, 1);
+    String proxy =
+        conf.get(Constants.PROXY_HOST) + ":" + conf.get(Constants.PROXY_PORT);
+    try {
+      fs = S3ATestUtils.createTestFileSystem(conf);
+      fail("Expected a connection error for proxy server at " + proxy);
+    } catch (AmazonClientException e) {
+      if (!e.getMessage().contains(proxy + " refused")) {
+        throw e;
+      }
+    }
+  }
+
+  @Test
+  public void TestProxyPortWithoutHost() throws Exception {
+    conf = new Configuration();
+    conf.setInt(Constants.MAX_ERROR_RETRIES, 2);
+    conf.setInt(Constants.PROXY_PORT, 1);
+    try {
+      fs = S3ATestUtils.createTestFileSystem(conf);
+      fail("Expected a proxy configuration error");
+    } catch (IllegalArgumentException e) {
+      String msg = e.toString();
+      if (!msg.contains(Constants.PROXY_HOST) &&
+          !msg.contains(Constants.PROXY_PORT)) {
+        throw e;
+      }
+    }
+  }
+
+  @Test
+  public void TestAutomaticProxyPortSelection() throws Exception {
+    conf = new Configuration();
+    conf.setInt(Constants.MAX_ERROR_RETRIES, 2);
+    conf.set(Constants.PROXY_HOST, "127.0.0.1");
+    conf.set(Constants.SECURE_CONNECTIONS, "true");
+    try {
+      fs = S3ATestUtils.createTestFileSystem(conf);
+      fail("Expected a connection error for proxy server");
+    } catch (AmazonClientException e) {
+      if (!e.getMessage().contains("443")) {
+        throw e;
+      }
+    }
+    conf.set(Constants.SECURE_CONNECTIONS, "false");
+    try {
+      fs = S3ATestUtils.createTestFileSystem(conf);
+      fail("Expected a connection error for proxy server");
+    } catch (AmazonClientException e) {
+      if (!e.getMessage().contains("80")) {
+        throw e;
+      }
+    }
+  }
+
+  @Test
+  public void TestUsernameInconsistentWithPassword() throws Exception {
+    conf = new Configuration();
+    conf.setInt(Constants.MAX_ERROR_RETRIES, 2);
+    conf.set(Constants.PROXY_HOST, "127.0.0.1");
+    conf.setInt(Constants.PROXY_PORT, 1);
+    conf.set(Constants.PROXY_USERNAME, "user");
+    try {
+      fs = S3ATestUtils.createTestFileSystem(conf);
+      fail("Expected a connection error for proxy server");
+    } catch (IllegalArgumentException e) {
+      String msg = e.toString();
+      if (!msg.contains(Constants.PROXY_USERNAME) &&
+          !msg.contains(Constants.PROXY_PASSWORD)) {
+        throw e;
+      }
+    }
+    conf = new Configuration();
+    conf.setInt(Constants.MAX_ERROR_RETRIES, 2);
+    conf.set(Constants.PROXY_HOST, "127.0.0.1");
+    conf.setInt(Constants.PROXY_PORT, 1);
+    conf.set(Constants.PROXY_PASSWORD, "password");
+    try {
+      fs = S3ATestUtils.createTestFileSystem(conf);
+      fail("Expected a connection error for proxy server");
+    } catch (IllegalArgumentException e) {
+      String msg = e.toString();
+      if (!msg.contains(Constants.PROXY_USERNAME) &&
+          !msg.contains(Constants.PROXY_PASSWORD)) {
+        throw e;
+      }
+    }
+  }
 }