diff --git a/lib/functions.php b/lib/functions.php
index a937b61..02d4f4e 100644
--- a/lib/functions.php
+++ b/lib/functions.php
@@ -91,9 +91,19 @@ function call(callable $functor, ...$args): Promise {
 /**
  * Registers a callback that will forward the failure reason to the Loop error handler if the promise fails.
  *
- * @param \Amp\Promise $promise
+ * @param \Amp\Promise|\React\Promise\PromiseInterface $promise
+ *
+ * @throws \TypeError If $promise is not an instance of \Amp\Promise or \React\Promise\PromiseInterface.
  */
-function rethrow(Promise $promise) {
+function rethrow($promise) {
+    if (!$promise instanceof Promise) {
+        if ($promise instanceof ReactPromise) {
+            $promise = adapt($promise);
+        } else {
+            throw new \TypeError("Must provide an instance of %s or %s", Promise::class, ReactPromise::class);
+        }
+    }
+
     $promise->when(function ($exception) {
         if ($exception) {
             throw $exception;
@@ -104,13 +114,22 @@ function rethrow(Promise $promise) {
 /**
  * Runs the event loop until the promise is resolved. Should not be called within a running event loop.
  *
- * @param \Amp\Promise $promise
+ * @param \Amp\Promise|\React\Promise\PromiseInterface $promise
  *
  * @return mixed Promise success value.
  *
+ * @throws \TypeError If $promise is not an instance of \Amp\Promise or \React\Promise\PromiseInterface.
  * @throws \Throwable Promise failure reason.
  */
-function wait(Promise $promise) {
+function wait($promise) {
+    if (!$promise instanceof Promise) {
+        if ($promise instanceof ReactPromise) {
+            $promise = adapt($promise);
+        } else {
+            throw new \TypeError("Must provide an instance of %s or %s", Promise::class, ReactPromise::class);
+        }
+    }
+
     $resolved = false;
     Loop::run(function () use (&$resolved, &$value, &$exception, $promise) {
         $promise->when(function ($e, $v) use (&$resolved, &$value, &$exception) {
@@ -135,12 +154,22 @@ function wait(Promise $promise) {
 /**
  * Pipe the promised value through the specified functor once it resolves.
  *
- * @param \Amp\Promise $promise
+ * @param \Amp\Promise|\React\Promise\PromiseInterface $promise
  * @param callable(mixed $value): mixed $functor
  *
  * @return \Amp\Promise
+ *
+ * @throws \TypeError If $promise is not an instance of \Amp\Promise or \React\Promise\PromiseInterface.
  */
-function pipe(Promise $promise, callable $functor): Promise {
+function pipe($promise, callable $functor): Promise {
+    if (!$promise instanceof Promise) {
+        if ($promise instanceof ReactPromise) {
+            $promise = adapt($promise);
+        } else {
+            throw new \TypeError("Must provide an instance of %s or %s", Promise::class, ReactPromise::class);
+        }
+    }
+
     $deferred = new Deferred;
 
     $promise->when(function ($exception, $value) use ($deferred, $functor) {
@@ -160,14 +189,24 @@ function pipe(Promise $promise, callable $functor): Promise {
 }
 
 /**
- * @param \Amp\Promise $promise
+ * @param \Amp\Promise|\React\Promise\PromiseInterface $promise
  * @param string $className Exception class name to capture. Given callback will only be invoked if the failure reason
  *     is an instance of the given exception class name.
  * @param callable(\Throwable $exception): mixed $functor
  *
  * @return \Amp\Promise
+ *
+ * @throws \TypeError If $promise is not an instance of \Amp\Promise or \React\Promise\PromiseInterface.
  */
-function capture(Promise $promise, string $className, callable $functor): Promise {
+function capture($promise, string $className, callable $functor): Promise {
+    if (!$promise instanceof Promise) {
+        if ($promise instanceof ReactPromise) {
+            $promise = adapt($promise);
+        } else {
+            throw new \TypeError("Must provide an instance of %s or %s", Promise::class, ReactPromise::class);
+        }
+    }
+
     $deferred = new Deferred;
 
     $promise->when(function ($exception, $value) use ($deferred, $className, $functor) {
@@ -197,12 +236,22 @@ function capture(Promise $promise, string $className, callable $functor): Promis
  * If the timeout expires before the promise is resolved, the returned promise fails with an instance of
  * \Amp\TimeoutException.
  *
- * @param \Amp\Promise $promise
+ * @param \Amp\Promise|\React\Promise\PromiseInterface $promise
  * @param int $timeout Timeout in milliseconds.
  *
  * @return \Amp\Promise
+ *
+ * @throws \TypeError If $promise is not an instance of \Amp\Promise or \React\Promise\PromiseInterface.
  */
-function timeout(Promise $promise, int $timeout): Promise {
+function timeout($promise, int $timeout): Promise {
+    if (!$promise instanceof Promise) {
+        if ($promise instanceof ReactPromise) {
+            $promise = adapt($promise);
+        } else {
+            throw new \TypeError("Must provide an instance of %s or %s", Promise::class, ReactPromise::class);
+        }
+    }
+
     $deferred = new Deferred;
     $resolved = false;
 
diff --git a/test/CaptureTest.php b/test/CaptureTest.php
index 25044ec..c06d7f5 100644
--- a/test/CaptureTest.php
+++ b/test/CaptureTest.php
@@ -6,6 +6,7 @@ use Amp;
 use Amp\Failure;
 use Amp\Success;
 use Amp\Promise;
+use function React\Promise\reject;
 
 class CaptureTest extends \PHPUnit\Framework\TestCase {
     public function testSuccessfulPromise() {
@@ -110,4 +111,33 @@ class CaptureTest extends \PHPUnit\Framework\TestCase {
         $this->assertFalse($invoked);
         $this->assertSame($exception, $reason);
     }
+
+    /**
+     * @depends testFailedPromise
+     */
+    public function testReactPromise() {
+        $invoked = false;
+        $callback = function ($exception) use (&$invoked, &$reason) {
+            $invoked = true;
+            $reason = $exception;
+            return -1;
+        };
+
+        $exception = new \Exception;
+
+        $promise = reject($exception);
+
+        $promise = Amp\capture($promise, \Exception::class, $callback);
+        $this->assertInstanceOf(Promise::class, $promise);
+
+        $callback = function ($exception, $value) use (&$result) {
+            $result = $value;
+        };
+
+        $promise->when($callback);
+
+        $this->assertTrue($invoked);
+        $this->assertSame($exception, $reason);
+        $this->assertSame(-1, $result);
+    }
 }
diff --git a/test/PipeTest.php b/test/PipeTest.php
index 83a9918..e6ffded 100644
--- a/test/PipeTest.php
+++ b/test/PipeTest.php
@@ -6,6 +6,7 @@ use Amp;
 use Amp\Failure;
 use Amp\Success;
 use Amp\Promise;
+use function React\Promise\resolve;
 
 class PipeTest extends \PHPUnit\Framework\TestCase {
     public function testSuccessfulPromise() {
@@ -81,4 +82,31 @@ class PipeTest extends \PHPUnit\Framework\TestCase {
         $this->assertTrue($invoked);
         $this->assertSame($exception, $reason);
     }
+
+    /**
+     * @depends testSuccessfulPromise
+     */
+    public function testReactPromise() {
+        $invoked = false;
+        $callback = function ($value) use (&$invoked) {
+            $invoked = true;
+            return $value + 1;
+        };
+
+        $value = 1;
+
+        $promise = resolve($value);
+
+        $promise = Amp\pipe($promise, $callback);
+        $this->assertInstanceOf(Promise::class, $promise);
+
+        $callback = function ($exception, $value) use (&$result) {
+            $result = $value;
+        };
+
+        $promise->when($callback);
+
+        $this->assertTrue($invoked);
+        $this->assertSame($value + 1, $result);
+    }
 }
diff --git a/test/RethrowTest.php b/test/RethrowTest.php
index 6302765..6812bc6 100644
--- a/test/RethrowTest.php
+++ b/test/RethrowTest.php
@@ -6,9 +6,10 @@ use Amp;
 use Amp\Failure;
 use Amp\Loop;
 use PHPUnit\Framework\TestCase;
+use function React\Promise\reject;
 
 class RethrowTest extends TestCase {
-    public function testWaitOnPendingPromise() {
+    public function testRethrow() {
         $exception = new \Exception;
 
         try {
@@ -24,4 +25,24 @@ class RethrowTest extends TestCase {
 
         $this->fail('Failed promise reason should be thrown from loop');
     }
+
+    /**
+     * @depends testRethrow
+     */
+    public function testReactPromise() {
+        $exception = new \Exception;
+
+        try {
+            Loop::run(function () use ($exception) {
+                $promise = reject($exception);
+
+                Amp\rethrow($promise);
+            });
+        } catch (\Exception $reason) {
+            $this->assertSame($exception, $reason);
+            return;
+        }
+
+        $this->fail('Failed promise reason should be thrown from loop');
+    }
 }
diff --git a/test/TimeoutTest.php b/test/TimeoutTest.php
index e34c9c6..dfe32cf 100644
--- a/test/TimeoutTest.php
+++ b/test/TimeoutTest.php
@@ -8,6 +8,7 @@ use Amp\Loop;
 use Amp\Pause;
 use Amp\Success;
 use Amp\Promise;
+use function React\Promise\resolve;
 
 class TimeoutTest extends \PHPUnit\Framework\TestCase {
     public function testSuccessfulPromise() {
@@ -89,4 +90,26 @@ class TimeoutTest extends \PHPUnit\Framework\TestCase {
 
         $this->assertInstanceOf(Amp\TimeoutException::class, $reason);
     }
+
+    /**
+     * @depends testSuccessfulPromise
+     */
+    public function testReactPromise() {
+        Loop::run(function () {
+            $value = 1;
+
+            $promise = resolve($value);
+
+            $promise = Amp\timeout($promise, 100);
+            $this->assertInstanceOf(Promise::class, $promise);
+
+            $callback = function ($exception, $value) use (&$result) {
+                $result = $value;
+            };
+
+            $promise->when($callback);
+
+            $this->assertSame($value, $result);
+        });
+    }
 }
diff --git a/test/WaitTest.php b/test/WaitTest.php
index 62f7788..cf82e53 100644
--- a/test/WaitTest.php
+++ b/test/WaitTest.php
@@ -8,6 +8,7 @@ use Amp\Failure;
 use Amp\Pause;
 use Amp\Success;
 use Amp\Loop;
+use function React\Promise\resolve;
 
 class WaitTest extends \PHPUnit\Framework\TestCase {
     public function testWaitOnSuccessfulPromise() {
@@ -59,4 +60,17 @@ class WaitTest extends \PHPUnit\Framework\TestCase {
 
         $result = Amp\wait($promise->promise());
     }
+
+    /**
+     * @depends testWaitOnSuccessfulPromise
+     */
+    public function testReactPromise() {
+        $value = 1;
+
+        $promise = resolve($value);
+
+        $result = Amp\wait($promise);
+
+        $this->assertSame($value, $result);
+    }
 }