diff --git a/src/Adapter/Swoole.php b/src/Adapter/Swoole.php
index 627c431..65308ba 100644
--- a/src/Adapter/Swoole.php
+++ b/src/Adapter/Swoole.php
@@ -208,7 +208,7 @@ private function executeRequest(
         RequestOptions $options,
         ?callable $chunkCallback
     ): Response {
-        if (!preg_match('~^https?://~i', $url)) {
+        if (!str_starts_with($url, 'http://') && !str_starts_with($url, 'https://')) {
             $url = 'http://' . $url;
         }
 
diff --git a/src/Client.php b/src/Client.php
index 50ac37a..ebbac89 100644
--- a/src/Client.php
+++ b/src/Client.php
@@ -53,6 +53,19 @@ public function __construct(?Adapter $adapter = null)
         $this->adapter = $adapter ?? new Curl();
     }
 
+    protected string $baseUrl = '';
+
+    public function setBaseUrl(string $baseUrl): self
+    {
+        $this->baseUrl = $baseUrl;
+        return $this;
+    }
+
+    public function getBaseUrl(): string
+    {
+        return $this->baseUrl;
+    }
+
     /**
      * @param string $key
      * @param string $value
@@ -166,7 +179,7 @@ public function setMaxRetries(int $maxRetries): self
      *
      * @param array<int> $flags
      * @return self
-    */
+     */
     public function setJsonEncodeFlags(array $flags): self
     {
         $this->jsonEncodeFlags = array_reduce($flags, function ($carry, $flag) {
@@ -289,6 +302,10 @@ public function fetch(
         ?int $timeoutMs = null,
         ?int $connectTimeoutMs = null,
     ): Response {
+        if (!empty($this->baseUrl) && !str_starts_with($url, 'http://') && !str_starts_with($url, 'https://')) {
+            $url = rtrim($this->baseUrl, '/') . '/' . ltrim($url, '/');
+        }
+
         if (!in_array($method, [self::METHOD_PATCH, self::METHOD_GET, self::METHOD_CONNECT, self::METHOD_DELETE, self::METHOD_POST, self::METHOD_HEAD, self::METHOD_OPTIONS, self::METHOD_PUT, self::METHOD_TRACE])) {
             throw new Exception("Unsupported HTTP method");
         }
diff --git a/tests/ClientTest.php b/tests/ClientTest.php
index 59843e3..c453a90 100644
--- a/tests/ClientTest.php
+++ b/tests/ClientTest.php
@@ -320,6 +320,146 @@ public function testSetGetUserAgent(): void
         $this->assertSame($userAgent, $client->getUserAgent());
     }
 
+    /**
+     * Test setting and getting the base URL.
+     * @return void
+     */
+    public function testSetGetBaseUrl(): void
+    {
+        $client = new Client();
+        $baseUrl = "http://localhost:8000";
+
+        $client->setBaseUrl($baseUrl);
+
+        $this->assertEquals($baseUrl, $client->getBaseUrl());
+    }
+
+    /**
+     * Test base URL prepending to relative URLs.
+     * @return void
+     */
+    public function testBaseUrlWithRelativePath(): void
+    {
+        $client = new Client();
+        $client->setBaseUrl('http://localhost:8000');
+
+        $resp = $client->fetch(
+            url: '',
+            method: Client::METHOD_GET
+        );
+
+        if ($resp->getStatusCode() === 200) {
+            /** @var array<string, mixed> $respData */
+            $respData = $resp->json();
+            $this->assertEquals($respData['method'], Client::METHOD_GET);
+            $this->assertEquals($respData['url'], 'localhost:8000');
+        } else {
+            echo "Please configure your PHP inbuilt SERVER";
+        }
+    }
+
+    /**
+     * Test base URL with path appending.
+     * @return void
+     */
+    public function testBaseUrlWithPath(): void
+    {
+        $client = new Client();
+        $client->setBaseUrl('http://localhost:8000');
+
+        $resp = $client->fetch(
+            url: 'redirect',
+            method: Client::METHOD_GET
+        );
+
+        if ($resp->getStatusCode() === 200) {
+            /** @var array<string, mixed> $respData */
+            $respData = $resp->json();
+            $this->assertEquals($respData['page'], "redirectedPage");
+        } else {
+            echo "Please configure your PHP inbuilt SERVER";
+        }
+    }
+
+    /**
+     * Test base URL doesn't interfere with absolute URLs.
+     * @return void
+     */
+    public function testBaseUrlWithAbsoluteUrl(): void
+    {
+        $client = new Client();
+        $client->setBaseUrl('http://example.com');
+
+        $resp = $client->fetch(
+            url: 'http://localhost:8000',
+            method: Client::METHOD_GET
+        );
+
+        if ($resp->getStatusCode() === 200) {
+            /** @var array<string, mixed> $respData */
+            $respData = $resp->json();
+            $this->assertEquals($respData['method'], Client::METHOD_GET);
+            $this->assertEquals($respData['url'], 'localhost:8000');
+        } else {
+            echo "Please configure your PHP inbuilt SERVER";
+        }
+    }
+
+    /**
+     * Test base URL with query parameters.
+     * @return void
+     */
+    public function testBaseUrlWithQuery(): void
+    {
+        $client = new Client();
+        $client->setBaseUrl('http://localhost:8000');
+
+        $resp = $client->fetch(
+            url: '',
+            method: Client::METHOD_GET,
+            query: [
+                'name' => 'John Doe',
+                'age' => '30',
+            ]
+        );
+
+        if ($resp->getStatusCode() === 200) {
+            /** @var array<string, mixed> $respData */
+            $respData = $resp->json();
+            $this->assertEquals($respData['method'], Client::METHOD_GET);
+            $this->assertEquals(
+                json_encode($respData['query']),
+                json_encode(['name' => 'John Doe', 'age' => '30'])
+            );
+        } else {
+            echo "Please configure your PHP inbuilt SERVER";
+        }
+    }
+
+    /**
+     * Test base URL with trailing slash normalization.
+     * @return void
+     */
+    public function testBaseUrlTrailingSlashNormalization(): void
+    {
+        $client = new Client();
+
+        // Test with trailing slash in base URL
+        $client->setBaseUrl('http://localhost:8000/');
+        $resp = $client->fetch(
+            url: '/redirect',
+            method: Client::METHOD_GET
+        );
+
+        if ($resp->getStatusCode() === 200) {
+            /** @var array<string, mixed> $respData */
+            $respData = $resp->json();
+            $this->assertEquals($respData['page'], "redirectedPage");
+        } else {
+            echo "Please configure your PHP inbuilt SERVER";
+        }
+    }
+
     /**
      * Data provider for testFetch
      * @return array<string, array<mixed>>