diff --git a/cli/tests/unit/net_test.ts b/cli/tests/unit/net_test.ts
index 652d07d7de..935a6f846b 100644
--- a/cli/tests/unit/net_test.ts
+++ b/cli/tests/unit/net_test.ts
@@ -425,6 +425,141 @@ Deno.test(
   },
 );
 
+Deno.test(
+  { permissions: { net: true }, ignore: true },
+  async function netUdpMulticastV4() {
+    const listener = Deno.listenDatagram({
+      hostname: "0.0.0.0",
+      port: 5353,
+      transport: "udp",
+      reuseAddress: true,
+    });
+
+    const membership = await listener.joinMulticastV4(
+      "224.0.0.251",
+      "127.0.0.1",
+    );
+
+    membership.setLoopback(true);
+    membership.setLoopback(false);
+    membership.setTTL(50);
+    membership.leave();
+    listener.close();
+  },
+);
+
+Deno.test(
+  { permissions: { net: true }, ignore: true },
+  async function netUdpMulticastV6() {
+    const listener = Deno.listenDatagram({
+      hostname: "::",
+      port: 5353,
+      transport: "udp",
+      reuseAddress: true,
+    });
+
+    const membership = await listener.joinMulticastV6(
+      "ff02::fb",
+      1,
+    );
+
+    membership.setLoopback(true);
+    membership.setLoopback(false);
+    membership.leave();
+    listener.close();
+  },
+);
+
+Deno.test(
+  { permissions: { net: true }, ignore: true },
+  async function netUdpSendReceiveMulticastv4() {
+    const alice = Deno.listenDatagram({
+      hostname: "0.0.0.0",
+      port: 5353,
+      transport: "udp",
+      reuseAddress: true,
+      loopback: true,
+    });
+
+    const bob = Deno.listenDatagram({
+      hostname: "0.0.0.0",
+      port: 5353,
+      transport: "udp",
+      reuseAddress: true,
+    });
+
+    const aliceMembership = await alice.joinMulticastV4(
+      "224.0.0.1",
+      "0.0.0.0",
+    );
+
+    const bobMembership = await bob.joinMulticastV4("224.0.0.1", "0.0.0.0");
+
+    const sent = new Uint8Array([1, 2, 3]);
+
+    await alice.send(sent, {
+      hostname: "224.0.0.1",
+      port: 5353,
+      transport: "udp",
+    });
+
+    const [recvd, remote] = await bob.receive();
+
+    assert(remote.transport === "udp");
+    assertEquals(remote.port, 5353);
+    assertEquals(recvd.length, 3);
+    assertEquals(1, recvd[0]);
+    assertEquals(2, recvd[1]);
+    assertEquals(3, recvd[2]);
+
+    aliceMembership.leave();
+    bobMembership.leave();
+
+    alice.close();
+    bob.close();
+  },
+);
+
+Deno.test(
+  { permissions: { net: true }, ignore: true },
+  async function netUdpMulticastLoopbackOption() {
+    // Must bind sender to an address that can send to the broadcast address on MacOS.
+    // Macos will give us error 49 when sending the broadcast packet if we omit hostname here.
+    const listener = Deno.listenDatagram({
+      port: 5353,
+      transport: "udp",
+      hostname: "0.0.0.0",
+      loopback: true,
+      reuseAddress: true,
+    });
+
+    const membership = await listener.joinMulticastV4(
+      "224.0.0.1",
+      "0.0.0.0",
+    );
+
+    // await membership.setLoopback(true);
+
+    const sent = new Uint8Array([1, 2, 3]);
+    const byteLength = await listener.send(sent, {
+      hostname: "224.0.0.1",
+      port: 5353,
+      transport: "udp",
+    });
+
+    assertEquals(byteLength, 3);
+    const [recvd, remote] = await listener.receive();
+    assert(remote.transport === "udp");
+    assertEquals(remote.port, 5353);
+    assertEquals(recvd.length, 3);
+    assertEquals(1, recvd[0]);
+    assertEquals(2, recvd[1]);
+    assertEquals(3, recvd[2]);
+    membership.leave();
+    listener.close();
+  },
+);
+
 Deno.test(
   { permissions: { net: true } },
   async function netUdpConcurrentSendReceive() {
diff --git a/cli/tsc/dts/lib.deno.unstable.d.ts b/cli/tsc/dts/lib.deno.unstable.d.ts
index ed7e682f12..62426ca35c 100644
--- a/cli/tsc/dts/lib.deno.unstable.d.ts
+++ b/cli/tsc/dts/lib.deno.unstable.d.ts
@@ -163,7 +163,7 @@ declare namespace Deno {
    */
   type ToNativeResultType<T extends NativeResultType = NativeResultType> =
     T extends NativeStructType ? BufferSource
-    : ToNativeResultTypeMap[Exclude<T, NativeStructType>];
+      : ToNativeResultTypeMap[Exclude<T, NativeStructType>];
 
   /** **UNSTABLE**: New API, yet to be vetted.
    *
@@ -225,7 +225,7 @@ declare namespace Deno {
    */
   type FromNativeResultType<T extends NativeResultType = NativeResultType> =
     T extends NativeStructType ? Uint8Array
-    : FromNativeResultTypeMap[Exclude<T, NativeStructType>];
+      : FromNativeResultTypeMap[Exclude<T, NativeStructType>];
 
   /** **UNSTABLE**: New API, yet to be vetted.
    *
@@ -850,6 +850,34 @@ declare namespace Deno {
     options: CreateHttpClientOptions,
   ): HttpClient;
 
+  /** **UNSTABLE**: New API, yet to be vetted.
+   *
+   * Represents membership of a IPv4 multicast group.
+   *
+   * @category Network
+   */
+  interface MulticastV4Membership {
+    /** Leaves the multicast group. */
+    leave: () => Promise<void>;
+    /** Sets the multicast loopback option. If enabled, multicast packets will be looped back to the local socket. */
+    setLoopback: (loopback: boolean) => Promise<void>;
+    /** Sets the time-to-live of outgoing multicast packets for this socket. */
+    setTTL: (ttl: number) => Promise<void>;
+  }
+
+  /** **UNSTABLE**: New API, yet to be vetted.
+   *
+   * Represents membership of a IPv6 multicast group.
+   *
+   * @category Network
+   */
+  interface MulticastV6Membership {
+    /** Leaves the multicast group. */
+    leave: () => Promise<void>;
+    /** Sets the multicast loopback option. If enabled, multicast packets will be looped back to the local socket. */
+    setLoopback: (loopback: boolean) => Promise<void>;
+  }
+
   /** **UNSTABLE**: New API, yet to be vetted.
    *
    * A generic transport listener for message-oriented protocols.
@@ -857,6 +885,18 @@ declare namespace Deno {
    * @category Network
    */
   export interface DatagramConn extends AsyncIterable<[Uint8Array, Addr]> {
+    /** Joins an IPv4 multicast group. */
+    joinMulticastV4(
+      address: string,
+      networkInterface: string,
+    ): Promise<MulticastV4Membership>;
+
+    /** Joins an IPv6 multicast group. */
+    joinMulticastV6(
+      address: string,
+      networkInterface: number,
+    ): Promise<MulticastV6Membership>;
+
     /** Waits for and resolves to the next message to the instance.
      *
      * Messages are received in the format of a tuple containing the data array
@@ -918,6 +958,11 @@ declare namespace Deno {
      *
      * @default {false} */
     reuseAddress?: boolean;
+
+    /** When `true`, sent multicast packets will be looped back to the local socket.
+     *
+     * @default {false} */
+    loopback?: boolean;
   }
 
   /** **UNSTABLE**: New API, yet to be vetted.
diff --git a/ext/net/01_net.js b/ext/net/01_net.js
index 8d8e34e569..81e13f0945 100644
--- a/ext/net/01_net.js
+++ b/ext/net/01_net.js
@@ -277,6 +277,64 @@ class Datagram {
     return this.#addr;
   }
 
+  async joinMulticastV4(addr, multiInterface) {
+    await core.opAsync(
+      "op_net_join_multi_v4_udp",
+      this.rid,
+      addr,
+      multiInterface,
+    );
+
+    return {
+      leave: () =>
+        core.opAsync(
+          "op_net_leave_multi_v4_udp",
+          this.rid,
+          addr,
+          multiInterface,
+        ),
+      setLoopback: (loopback) =>
+        core.opAsync(
+          "op_net_set_multi_loopback_udp",
+          this.rid,
+          true,
+          loopback,
+        ),
+      setTTL: (ttl) =>
+        core.opAsync(
+          "op_net_set_multi_ttl_udp",
+          this.rid,
+          ttl,
+        ),
+    };
+  }
+
+  async joinMulticastV6(addr, multiInterface) {
+    await core.opAsync(
+      "op_net_join_multi_v6_udp",
+      this.rid,
+      addr,
+      multiInterface,
+    );
+
+    return {
+      leave: () =>
+        core.opAsync(
+          "op_net_leave_multi_v6_udp",
+          this.rid,
+          addr,
+          multiInterface,
+        ),
+      setLoopback: (loopback) =>
+        core.opAsync(
+          "op_net_set_multi_loopback_udp",
+          this.rid,
+          false,
+          loopback,
+        ),
+    };
+  }
+
   async receive(p) {
     const buf = p || new Uint8Array(this.bufSize);
     let nread;
@@ -383,6 +441,7 @@ function createListenDatagram(udpOpFn, unixOpFn) {
             port: args.port,
           },
           args.reuseAddress ?? false,
+          args.loopback ?? false,
         );
         addr.transport = "udp";
         return new Datagram(rid, addr);
diff --git a/ext/net/lib.rs b/ext/net/lib.rs
index 00833b53c4..f812bf60bc 100644
--- a/ext/net/lib.rs
+++ b/ext/net/lib.rs
@@ -86,6 +86,12 @@ deno_core::extension!(deno_net,
     ops::op_node_unstable_net_listen_udp<P>,
     ops::op_net_recv_udp,
     ops::op_net_send_udp<P>,
+    ops::op_net_join_multi_v4_udp<P>,
+    ops::op_net_join_multi_v6_udp<P>,
+    ops::op_net_leave_multi_v4_udp<P>,
+    ops::op_net_leave_multi_v6_udp<P>,
+    ops::op_net_set_multi_loopback_udp<P>,
+    ops::op_net_set_multi_ttl_udp<P>,
     ops::op_dns_resolve<P>,
     ops::op_set_nodelay,
     ops::op_set_keepalive,
diff --git a/ext/net/ops.rs b/ext/net/ops.rs
index c094ddac2b..8e7263753a 100644
--- a/ext/net/ops.rs
+++ b/ext/net/ops.rs
@@ -28,8 +28,11 @@ use socket2::Socket;
 use socket2::Type;
 use std::borrow::Cow;
 use std::cell::RefCell;
+use std::net::Ipv4Addr;
+use std::net::Ipv6Addr;
 use std::net::SocketAddr;
 use std::rc::Rc;
+use std::str::FromStr;
 use tokio::net::TcpListener;
 use tokio::net::TcpStream;
 use tokio::net::UdpSocket;
@@ -155,6 +158,151 @@ where
   Ok(nwritten)
 }
 
+#[op]
+async fn op_net_join_multi_v4_udp<NP>(
+  state: Rc<RefCell<OpState>>,
+  rid: ResourceId,
+  address: String,
+  multi_interface: String,
+) -> Result<(), AnyError>
+where
+  NP: NetPermissions + 'static,
+{
+  let resource = state
+    .borrow_mut()
+    .resource_table
+    .get::<UdpSocketResource>(rid)
+    .map_err(|_| bad_resource("Socket has been closed"))?;
+  let socket = RcRef::map(&resource, |r| &r.socket).borrow().await;
+
+  let addr = Ipv4Addr::from_str(address.as_str())?;
+  let interface_addr = Ipv4Addr::from_str(multi_interface.as_str())?;
+
+  socket.join_multicast_v4(addr, interface_addr)?;
+
+  Ok(())
+}
+
+#[op]
+async fn op_net_join_multi_v6_udp<NP>(
+  state: Rc<RefCell<OpState>>,
+  rid: ResourceId,
+  address: String,
+  multi_interface: u32,
+) -> Result<(), AnyError>
+where
+  NP: NetPermissions + 'static,
+{
+  let resource = state
+    .borrow_mut()
+    .resource_table
+    .get::<UdpSocketResource>(rid)
+    .map_err(|_| bad_resource("Socket has been closed"))?;
+  let socket = RcRef::map(&resource, |r| &r.socket).borrow().await;
+
+  let addr = Ipv6Addr::from_str(address.as_str())?;
+
+  socket.join_multicast_v6(&addr, multi_interface)?;
+
+  Ok(())
+}
+
+#[op]
+async fn op_net_leave_multi_v4_udp<NP>(
+  state: Rc<RefCell<OpState>>,
+  rid: ResourceId,
+  address: String,
+  multi_interface: String,
+) -> Result<(), AnyError>
+where
+  NP: NetPermissions + 'static,
+{
+  let resource = state
+    .borrow_mut()
+    .resource_table
+    .get::<UdpSocketResource>(rid)
+    .map_err(|_| bad_resource("Socket has been closed"))?;
+  let socket = RcRef::map(&resource, |r| &r.socket).borrow().await;
+
+  let addr = Ipv4Addr::from_str(address.as_str())?;
+  let interface_addr = Ipv4Addr::from_str(multi_interface.as_str())?;
+
+  socket.leave_multicast_v4(addr, interface_addr)?;
+
+  Ok(())
+}
+
+#[op]
+async fn op_net_leave_multi_v6_udp<NP>(
+  state: Rc<RefCell<OpState>>,
+  rid: ResourceId,
+  address: String,
+  multi_interface: u32,
+) -> Result<(), AnyError>
+where
+  NP: NetPermissions + 'static,
+{
+  let resource = state
+    .borrow_mut()
+    .resource_table
+    .get::<UdpSocketResource>(rid)
+    .map_err(|_| bad_resource("Socket has been closed"))?;
+  let socket = RcRef::map(&resource, |r| &r.socket).borrow().await;
+
+  let addr = Ipv6Addr::from_str(address.as_str())?;
+
+  socket.leave_multicast_v6(&addr, multi_interface)?;
+
+  Ok(())
+}
+
+#[op]
+async fn op_net_set_multi_loopback_udp<NP>(
+  state: Rc<RefCell<OpState>>,
+  rid: ResourceId,
+  is_v4_membership: bool,
+  loopback: bool,
+) -> Result<(), AnyError>
+where
+  NP: NetPermissions + 'static,
+{
+  let resource = state
+    .borrow_mut()
+    .resource_table
+    .get::<UdpSocketResource>(rid)
+    .map_err(|_| bad_resource("Socket has been closed"))?;
+  let socket = RcRef::map(&resource, |r| &r.socket).borrow().await;
+
+  if is_v4_membership {
+    socket.set_multicast_loop_v4(loopback)?
+  } else {
+    socket.set_multicast_loop_v6(loopback)?;
+  }
+
+  Ok(())
+}
+
+#[op]
+async fn op_net_set_multi_ttl_udp<NP>(
+  state: Rc<RefCell<OpState>>,
+  rid: ResourceId,
+  ttl: u32,
+) -> Result<(), AnyError>
+where
+  NP: NetPermissions + 'static,
+{
+  let resource = state
+    .borrow_mut()
+    .resource_table
+    .get::<UdpSocketResource>(rid)
+    .map_err(|_| bad_resource("Socket has been closed"))?;
+  let socket = RcRef::map(&resource, |r| &r.socket).borrow().await;
+
+  socket.set_multicast_ttl_v4(ttl)?;
+
+  Ok(())
+}
+
 #[op]
 pub async fn op_net_connect_tcp<NP>(
   state: Rc<RefCell<OpState>>,
@@ -266,6 +414,7 @@ fn net_listen_udp<NP>(
   state: &mut OpState,
   addr: IpAddr,
   reuse_address: bool,
+  loopback: bool,
 ) -> Result<(ResourceId, IpAddr), AnyError>
 where
   NP: NetPermissions + 'static,
@@ -301,9 +450,18 @@ where
   let socket_addr = socket2::SockAddr::from(addr);
   socket_tmp.bind(&socket_addr)?;
   socket_tmp.set_nonblocking(true)?;
+
   // Enable messages to be sent to the broadcast address (255.255.255.255) by default
   socket_tmp.set_broadcast(true)?;
+
+  if domain == Domain::IPV4 {
+    socket_tmp.set_multicast_loop_v4(loopback)?;
+  } else {
+    socket_tmp.set_multicast_loop_v6(loopback)?;
+  }
+
   let std_socket: std::net::UdpSocket = socket_tmp.into();
+
   let socket = UdpSocket::from_std(std_socket)?;
   let local_addr = socket.local_addr()?;
   let socket_resource = UdpSocketResource {
@@ -320,12 +478,13 @@ fn op_net_listen_udp<NP>(
   state: &mut OpState,
   addr: IpAddr,
   reuse_address: bool,
+  loopback: bool,
 ) -> Result<(ResourceId, IpAddr), AnyError>
 where
   NP: NetPermissions + 'static,
 {
   super::check_unstable(state, "Deno.listenDatagram");
-  net_listen_udp::<NP>(state, addr, reuse_address)
+  net_listen_udp::<NP>(state, addr, reuse_address, loopback)
 }
 
 #[op]
@@ -333,11 +492,12 @@ fn op_node_unstable_net_listen_udp<NP>(
   state: &mut OpState,
   addr: IpAddr,
   reuse_address: bool,
+  loopback: bool,
 ) -> Result<(ResourceId, IpAddr), AnyError>
 where
   NP: NetPermissions + 'static,
 {
-  net_listen_udp::<NP>(state, addr, reuse_address)
+  net_listen_udp::<NP>(state, addr, reuse_address, loopback)
 }
 
 #[derive(Serialize, Eq, PartialEq, Debug)]