diff --git a/Libraries/LibWeb/CMakeLists.txt b/Libraries/LibWeb/CMakeLists.txt
index 07988c602d0..3d853c53aa8 100644
--- a/Libraries/LibWeb/CMakeLists.txt
+++ b/Libraries/LibWeb/CMakeLists.txt
@@ -664,6 +664,7 @@ set(SOURCES
     Streams/AbstractOperations.cpp
     Streams/ByteLengthQueuingStrategy.cpp
     Streams/CountQueuingStrategy.cpp
+    Streams/GenericTransformStream.cpp
     Streams/ReadableByteStreamController.cpp
     Streams/ReadableStream.cpp
     Streams/ReadableStreamBYOBReader.cpp
diff --git a/Libraries/LibWeb/Streams/GenericTransformStream.cpp b/Libraries/LibWeb/Streams/GenericTransformStream.cpp
new file mode 100644
index 00000000000..ed720eba3f0
--- /dev/null
+++ b/Libraries/LibWeb/Streams/GenericTransformStream.cpp
@@ -0,0 +1,40 @@
+/*
+ * Copyright (c) 2024, Tim Flynn <trflynn89@ladybird.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibWeb/Streams/GenericTransformStream.h>
+#include <LibWeb/Streams/ReadableStream.h>
+#include <LibWeb/Streams/TransformStream.h>
+#include <LibWeb/Streams/WritableStream.h>
+
+namespace Web::Streams {
+
+GenericTransformStreamMixin::GenericTransformStreamMixin(GC::Ref<TransformStream> transform)
+    : m_transform(transform)
+{
+}
+
+GenericTransformStreamMixin::~GenericTransformStreamMixin() = default;
+
+void GenericTransformStreamMixin::visit_edges(GC::Cell::Visitor& visitor)
+{
+    visitor.visit(m_transform);
+}
+
+// https://streams.spec.whatwg.org/#dom-generictransformstream-readable
+GC::Ref<ReadableStream> GenericTransformStreamMixin::readable()
+{
+    // The readable getter steps are to return this's transform.[[readable]].
+    return m_transform->readable();
+}
+
+// https://streams.spec.whatwg.org/#dom-generictransformstream-writable
+GC::Ref<WritableStream> GenericTransformStreamMixin::writable()
+{
+    // The writable getter steps are to return this's transform.[[writable]].
+    return m_transform->writable();
+}
+
+}
diff --git a/Libraries/LibWeb/Streams/GenericTransformStream.h b/Libraries/LibWeb/Streams/GenericTransformStream.h
new file mode 100644
index 00000000000..cb7ae5f1d6d
--- /dev/null
+++ b/Libraries/LibWeb/Streams/GenericTransformStream.h
@@ -0,0 +1,30 @@
+/*
+ * Copyright (c) 2024, Tim Flynn <trflynn89@ladybird.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <LibGC/Cell.h>
+#include <LibGC/Ptr.h>
+#include <LibWeb/Forward.h>
+
+namespace Web::Streams {
+
+class GenericTransformStreamMixin {
+public:
+    virtual ~GenericTransformStreamMixin();
+
+    GC::Ref<ReadableStream> readable();
+    GC::Ref<WritableStream> writable();
+
+protected:
+    explicit GenericTransformStreamMixin(GC::Ref<TransformStream>);
+    void visit_edges(GC::Cell::Visitor&);
+
+    // https://streams.spec.whatwg.org/#generictransformstream-transform
+    GC::Ref<TransformStream> m_transform;
+};
+
+}
diff --git a/Libraries/LibWeb/Streams/GenericTransformStream.idl b/Libraries/LibWeb/Streams/GenericTransformStream.idl
new file mode 100644
index 00000000000..2bbec637bc1
--- /dev/null
+++ b/Libraries/LibWeb/Streams/GenericTransformStream.idl
@@ -0,0 +1,7 @@
+#import <Streams/ReadableStream.idl>
+#import <Streams/WritableStream.idl>
+
+interface mixin GenericTransformStream {
+    readonly attribute ReadableStream readable;
+    readonly attribute WritableStream writable;
+};