diff --git a/misc/multiaddr/Cargo.toml b/misc/multiaddr/Cargo.toml
index 2b876e31..178494cc 100644
--- a/misc/multiaddr/Cargo.toml
+++ b/misc/multiaddr/Cargo.toml
@@ -9,8 +9,10 @@ readme = "README.md"
 version = "0.3.0"
 
 [dependencies]
+arrayref = "0.3"
 bs58 = "0.2.0"
 byteorder = "0.4"
+data-encoding = "2.1"
 multihash = { path = "../multihash" }
 serde = "1.0.70"
 unsigned-varint = "0.1"
diff --git a/misc/multiaddr/src/lib.rs b/misc/multiaddr/src/lib.rs
index 5e4d8445..e7c16266 100644
--- a/misc/multiaddr/src/lib.rs
+++ b/misc/multiaddr/src/lib.rs
@@ -3,8 +3,11 @@
 ///! Implementation of [multiaddr](https://github.com/jbenet/multiaddr)
 ///! in Rust.
 
+#[macro_use]
+extern crate arrayref;
 extern crate bs58;
 extern crate byteorder;
+extern crate data_encoding;
 extern crate serde;
 extern crate unsigned_varint;
 pub extern crate multihash;
diff --git a/misc/multiaddr/src/protocol.rs b/misc/multiaddr/src/protocol.rs
index a610cd4d..f12ccca5 100644
--- a/misc/multiaddr/src/protocol.rs
+++ b/misc/multiaddr/src/protocol.rs
@@ -1,5 +1,6 @@
 use bs58;
-use byteorder::{BigEndian, ReadBytesExt, WriteBytesExt};
+use byteorder::{BigEndian, ByteOrder, ReadBytesExt, WriteBytesExt};
+use data_encoding::BASE32;
 use multihash::Multihash;
 use std::{
     borrow::Cow,
@@ -50,7 +51,7 @@ pub enum Protocol<'a> {
     P2pWebRtcStar,
     P2pWebSocketStar,
     Memory,
-    Onion(Cow<'a, [u8]>),
+    Onion(Cow<'a, [u8; 10]>, u16),
     P2p(Multihash),
     P2pCircuit,
     Quic,
@@ -121,7 +122,11 @@ impl<'a> Protocol<'a> {
             }
             "http" => Ok(Protocol::Http),
             "https" => Ok(Protocol::Https),
-            "onion" => unimplemented!(), // FIXME
+            "onion" =>
+                iter.next()
+                    .ok_or(Error::InvalidProtocolString)
+                    .and_then(|s| read_onion(&s.to_uppercase()))
+                    .map(|(a, p)| Protocol::Onion(Cow::Owned(a), p)),
             "quic" => Ok(Protocol::Quic),
             "ws" => Ok(Protocol::Ws),
             "wss" => Ok(Protocol::Wss),
@@ -191,7 +196,11 @@ impl<'a> Protocol<'a> {
             P2P_WEBRTC_STAR => Ok((Protocol::P2pWebRtcStar, input)),
             P2P_WEBSOCKET_STAR => Ok((Protocol::P2pWebSocketStar, input)),
             MEMORY => Ok((Protocol::Memory, input)),
-            ONION => unimplemented!(), // FIXME
+            ONION => {
+                let (data, rest) = split_at(12, input)?;
+                let port = BigEndian::read_u16(&data[10 ..]);
+                Ok((Protocol::Onion(Cow::Borrowed(array_ref!(data, 0, 10)), port), rest))
+            }
             P2P => {
                 let (n, input) = decode::usize(input)?;
                 let (data, rest) = split_at(n, input)?;
@@ -285,7 +294,11 @@ impl<'a> Protocol<'a> {
                 w.write_all(encode::usize(bytes.len(), &mut encode::usize_buffer()))?;
                 w.write_all(&bytes)?
             }
-            Protocol::Onion(_) => unimplemented!(), // FIXME
+            Protocol::Onion(addr, port) => {
+                w.write_all(encode::u32(ONION, &mut buf))?;
+                w.write_all(addr.as_ref())?;
+                w.write_u16::<BigEndian>(*port)?
+            }
             Protocol::Quic => w.write_all(encode::u32(QUIC, &mut buf))?,
             Protocol::Utp => w.write_all(encode::u32(UTP, &mut buf))?,
             Protocol::Udt => w.write_all(encode::u32(UDT, &mut buf))?,
@@ -317,7 +330,7 @@ impl<'a> Protocol<'a> {
             P2pWebRtcStar => P2pWebRtcStar,
             P2pWebSocketStar => P2pWebSocketStar,
             Memory => Memory,
-            Onion(cow) => Onion(Cow::Owned(cow.into_owned())),
+            Onion(addr, port) => Onion(Cow::Owned(addr.into_owned()), port),
             P2p(a) => P2p(a),
             P2pCircuit => P2pCircuit,
             Quic => Quic,
@@ -348,7 +361,10 @@ impl<'a> fmt::Display for Protocol<'a> {
             P2pWebRtcStar => f.write_str("/p2p-webrtc-star"),
             P2pWebSocketStar => f.write_str("/p2p-websocket-star"),
             Memory => f.write_str("/memory"),
-            Onion(_) => unimplemented!(), // FIXME!
+            Onion(addr, port) => {
+                let s = BASE32.encode(addr.as_ref());
+                write!(f, "/onion/{}:{}", s.to_lowercase(), port)
+            }
             P2p(c) => write!(f, "/p2p/{}", bs58::encode(c.as_bytes()).into_string()),
             P2pCircuit => f.write_str("/p2p-circuit"),
             Quic => f.write_str("/quic"),
@@ -378,3 +394,35 @@ impl<'a> From<Ipv6Addr> for Protocol<'a> {
     }
 }
 
+// Parse a version 2 onion address and return its binary representation.
+//
+// Format: <base-32 address> ":" <port number>
+fn read_onion(s: &str) -> Result<([u8; 10], u16)> {
+    let mut parts = s.split(':');
+
+    // address part (without ".onion")
+    let b32 = parts.next().ok_or(Error::InvalidMultiaddr)?;
+    if b32.len() != 16 {
+        return Err(Error::InvalidMultiaddr)
+    }
+
+    // port number
+    let port = parts.next()
+        .ok_or(Error::InvalidMultiaddr)
+        .and_then(|p| str::parse(p).map_err(From::from))?;
+
+    // nothing else expected
+    if parts.next().is_some() {
+        return Err(Error::InvalidMultiaddr)
+    }
+
+    if 10 != BASE32.decode_len(b32.len()).map_err(|_| Error::InvalidMultiaddr)? {
+        return Err(Error::InvalidMultiaddr)
+    }
+
+    let mut buf = [0u8; 10];
+    BASE32.decode_mut(b32.as_bytes(), &mut buf).map_err(|_| Error::InvalidMultiaddr)?;
+
+    Ok((buf, port))
+}
+
diff --git a/misc/multiaddr/tests/lib.rs b/misc/multiaddr/tests/lib.rs
index 5c7c8634..4ee5ea6b 100644
--- a/misc/multiaddr/tests/lib.rs
+++ b/misc/multiaddr/tests/lib.rs
@@ -59,7 +59,7 @@ struct Proto(Protocol<'static>);
 impl Arbitrary for Proto {
     fn arbitrary<G: Gen>(g: &mut G) -> Self {
         use Protocol::*;
-        match g.gen_range(0, 22) { // TODO: Add Protocol::Quic
+        match g.gen_range(0, 23) { // TODO: Add Protocol::Quic
              0 => Proto(Dccp(g.gen())),
              1 => Proto(Dns4(Cow::Owned(SubString::arbitrary(g).0))),
              2 => Proto(Dns6(Cow::Owned(SubString::arbitrary(g).0))),
@@ -83,6 +83,11 @@ impl Arbitrary for Proto {
             19 => Proto(Utp),
             20 => Proto(Ws),
             21 => Proto(Wss),
+            22 => {
+                let mut a = [0; 10];
+                g.fill(&mut a);
+                Proto(Onion(Cow::Owned(a), g.gen()))
+            }
              _ => panic!("outside range")
         }
     }