diff --git a/src/Request.php b/src/Request.php
index f33faeb..b113ba6 100644
--- a/src/Request.php
+++ b/src/Request.php
@@ -1,6 +1,7 @@
 <?php
 namespace Gt\Http;
 
+use Psr\Http\Message\StreamInterface;
 use Psr\Http\Message\RequestInterface;
 use Psr\Http\Message\UriInterface;
 use Gt\Http\Header\RequestHeaders;
@@ -94,4 +95,24 @@ public function withUri(UriInterface $uri, bool$preserveHost = false):self {
 		$clone->uri = $uri;
 		return $clone;
 	}
+
+	/** @inheritDoc */
+	public function withBody(StreamInterface|FormData $body):self {
+		if($body instanceof FormData) {
+			$stream = new Stream();
+			$stream->write((string)$body);
+			$stream->rewind();
+
+			$clone = clone $this;
+			$clone->stream = $stream;
+			if(!$clone->headers->contains("Content-Type")) {
+				$clone->headers->set("Content-Type", "application/x-www-form-urlencoded");
+			}
+			return $clone;
+		}
+
+		$clone = clone $this;
+		$clone->stream = $body;
+		return $clone;
+	}
 }
diff --git a/test/phpunit/RequestTest.php b/test/phpunit/RequestTest.php
index 913a191..b833791 100644
--- a/test/phpunit/RequestTest.php
+++ b/test/phpunit/RequestTest.php
@@ -1,6 +1,7 @@
 <?php
 namespace Gt\Http\Test;
 
+use Gt\Http\FormData;
 use Gt\Http\Header\RequestHeaders;
 use Gt\Http\InvalidRequestMethodHttpException;
 use Gt\Http\Request;
@@ -97,6 +98,23 @@ public function testWithUriNewHost() {
 		$req->withUri(self::getUriMock("https://example2.com/something"));
 	}
 
+	public function testWithFormDataBodyAutomaticallySetsContentTypeHeader():void {
+		$formData = new FormData();
+		$formData->append("key", "value");
+
+		$request = new Request(
+			"POST",
+			self::getUriMock("/"),
+			new RequestHeaders()
+		);
+
+		$request = $request->withBody($formData);
+		self::assertSame(
+			"application/x-www-form-urlencoded",
+			$request->getHeaderLine("Content-Type")
+		);
+	}
+
 	/** @return MockObject|Uri */
 	protected function getUriMock(string $uriPath = ""):MockObject {
 		$partPath = parse_url($uriPath, PHP_URL_PATH);