diff --git a/.appveyor.yml b/.appveyor.yml
index 4b257d388..5e9ed4121 100644
--- a/.appveyor.yml
+++ b/.appveyor.yml
@@ -35,6 +35,9 @@ test_script:
   #- if [%TOOLCHAIN%]==[nightly] (
   #    cargo test --features nightly
   #  )
+  - if [%TOOLCHAIN%]==[nightly] (
+      cargo test -p tsukuyomi-codegen
+    )
   # contrib
   - cargo test -p tsukuyomi-juniper
   - if [%TOOLCHAIN%]==[nightly] (
diff --git a/.travis.yml b/.travis.yml
index 81f2c38fa..70a819fe1 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -81,6 +81,7 @@ matrix:
         - cargo test
         - cargo test --no-default-features
         #- cargo test --features nightly
+        - cargo test -p tsukuyomi-codegen
         # contrib
         - cargo test -p tsukuyomi-juniper
         # doctest
@@ -104,6 +105,7 @@ matrix:
       script:
         - cargo clean
         - cargo doc
+        #- cargo doc -p tsukuyomi-codegen
         - cargo doc -p tsukuyomi-juniper
         - rm -f target/doc/.lock
       deploy:
diff --git a/Cargo.toml b/Cargo.toml
index dedfddbd1..f73902e32 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -30,10 +30,12 @@ maintenance = { status = "actively-developed" }
 [workspace]
 members = [
   "doctest",
+  "tsukuyomi-codegen",
   "tsukuyomi-juniper",
 
   "examples/async-await",
   "examples/basic",
+  "examples/codegen",
   "examples/diesel",
   "examples/git-server",
   "examples/json",
@@ -64,6 +66,8 @@ serde = { version = "1.0.66", features = ["derive"] }
 serde_json = "1.0.20"
 state = "0.4"
 
+tsukuyomi-codegen = { version = "0.1.0", path = "tsukuyomi-codegen", optional = true }
+
 [dev-dependencies]
 matches = "0.1.6"
 time = "0.1.40"
@@ -75,4 +79,5 @@ tokio-uds = "0.2.0"
 default = []
 secure = ["cookie/secure"]
 tls = ["rustls", "tokio-rustls"]
-# nightly = []
+codegen = ["tsukuyomi-codegen"]
+nightly = ["tsukuyomi-codegen/nightly"]
diff --git a/examples/codegen/Cargo.toml b/examples/codegen/Cargo.toml
new file mode 100644
index 000000000..0156f1ad0
--- /dev/null
+++ b/examples/codegen/Cargo.toml
@@ -0,0 +1,14 @@
+[package]
+name = "example-codegen"
+version = "0.0.0"
+authors = ["Yusuke Sasaki <yusuke.sasaki.nuem@gmail.com>"]
+publish = false
+
+[[bin]]
+name = "codegen"
+path = "src/main.rs"
+doc = false
+
+[dependencies]
+tsukuyomi = { path = "../..", features = ["codegen"] }
+futures-await = "0.1.1"
diff --git a/examples/codegen/src/main.rs b/examples/codegen/src/main.rs
new file mode 100644
index 000000000..3e1ecf5c3
--- /dev/null
+++ b/examples/codegen/src/main.rs
@@ -0,0 +1,38 @@
+#![feature(proc_macro)]
+#![feature(proc_macro_non_items, generators)] // for futures-await
+
+extern crate futures_await as futures;
+extern crate tsukuyomi;
+
+use futures::prelude::{await, Future};
+use tsukuyomi::prelude::handler;
+use tsukuyomi::{App, Error, Input, Handler};
+
+#[handler]
+fn ready_handler() -> &'static str {
+    "Hello, Tsukuyomi.\n"
+}
+
+#[handler(async)]
+fn async_handler(input: &mut Input) -> impl Future<Item = String, Error = Error> + Send + 'static {
+    input.body_mut().read_all().convert_to()
+}
+
+#[handler(await)]
+fn await_handler() -> tsukuyomi::Result<String> {
+    let read_all = Input::with_current(|input| input.body_mut().read_all());
+    let data: String = await!(read_all.convert_to())?;
+    Ok(format!("Received: {}", data))
+}
+
+fn main() -> tsukuyomi::AppResult<()> {
+    let app = App::builder()
+        .mount("/", |m| {
+            m.get("/ready").handle(Handler::new(ready_handler));
+            m.post("/async").handle(Handler::new(async_handler));
+            m.post("/await").handle(Handler::new(await_handler));
+        })
+        .finish()?;
+
+    tsukuyomi::run(app)
+}
diff --git a/src/handler.rs b/src/handler.rs
index 9776eeaff..86c6c4c63 100644
--- a/src/handler.rs
+++ b/src/handler.rs
@@ -18,7 +18,8 @@ impl fmt::Debug for Handler {
 }
 
 impl Handler {
-    fn new(handler: impl Fn(&mut Input) -> Handle + Send + Sync + 'static) -> Handler {
+    #[doc(hidden)]
+    pub fn new(handler: impl Fn(&mut Input) -> Handle + Send + Sync + 'static) -> Handler {
         Handler(Box::new(handler))
     }
 
@@ -179,7 +180,8 @@ impl Handle {
         Handle::ready(Err(err.into()))
     }
 
-    fn ready(result: Result<Output, Error>) -> Handle {
+    #[doc(hidden)]
+    pub fn ready(result: Result<Output, Error>) -> Handle {
         Handle(HandleKind::Ready(Some(result)))
     }
 
@@ -193,6 +195,19 @@ impl Handle {
         })))
     }
 
+    #[doc(hidden)]
+    pub fn async_responder<F>(mut future: F) -> Handle
+    where
+        F: Future + Send + 'static,
+        F::Item: Responder,
+        Error: From<F::Error>,
+    {
+        Handle(HandleKind::Async(Box::new(move |input| {
+            let x = try_ready!(input.with_set_current(|| future.poll()));
+            x.respond_to(input).map(Async::Ready)
+        })))
+    }
+
     pub(crate) fn poll_ready(&mut self, input: &mut Input) -> Poll<Output, Error> {
         match self.0 {
             HandleKind::Ready(ref mut res) => res.take().expect("this future has already polled").map(Async::Ready),
diff --git a/src/lib.rs b/src/lib.rs
index 3c0fd2ea2..2f35fd8bb 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -7,6 +7,7 @@
 #![deny(unused_extern_crates)]
 #![deny(warnings)]
 #![deny(bare_trait_objects)]
+#![cfg_attr(feature = "codegen", feature(use_extern_macros))]
 
 extern crate bytes;
 extern crate cookie;
@@ -38,6 +39,9 @@ extern crate rustls;
 #[cfg(feature = "tls")]
 extern crate tokio_rustls;
 
+#[cfg(feature = "codegen")]
+extern crate tsukuyomi_codegen;
+
 pub mod app;
 pub mod error;
 pub mod handler;
@@ -72,3 +76,9 @@ pub fn run(app: App) -> AppResult<()> {
     server.serve();
     Ok(())
 }
+
+#[allow(missing_docs)]
+pub mod prelude {
+    #[cfg(feature = "codegen")]
+    pub use tsukuyomi_codegen::handler;
+}
diff --git a/tsukuyomi-codegen/Cargo.toml b/tsukuyomi-codegen/Cargo.toml
new file mode 100644
index 000000000..0a5634c73
--- /dev/null
+++ b/tsukuyomi-codegen/Cargo.toml
@@ -0,0 +1,21 @@
+[package]
+name = "tsukuyomi-codegen"
+version = "0.1.0"
+authors = ["Yusuke Sasaki <yusuke.sasaki.nuem@gmail.com>"]
+publish = false
+
+[lib]
+proc-macro = true
+
+[dependencies]
+proc-macro2 = "0.4.6"
+syn = { version = "0.14.4", features = ["full", "extra-traits"] }
+quote = "0.6.3"
+
+[dev-dependencies]
+tsukuyomi = { version = "0.2.0", path = ".." }
+futures = "0.1.21"
+futures-await = "0.1.1"
+
+[features]
+nightly = ["proc-macro2/nightly"]
diff --git a/tsukuyomi-codegen/src/lib.rs b/tsukuyomi-codegen/src/lib.rs
new file mode 100644
index 000000000..d0eb83a7b
--- /dev/null
+++ b/tsukuyomi-codegen/src/lib.rs
@@ -0,0 +1,187 @@
+//! Code generation support for Tsukuyomi.
+
+#![feature(proc_macro, use_extern_macros)]
+
+extern crate proc_macro;
+extern crate proc_macro2;
+#[macro_use]
+extern crate syn;
+extern crate quote;
+
+use proc_macro::TokenStream;
+use proc_macro2::Span;
+use quote::*;
+
+macro_rules! try_quote {
+    ($e:expr) => {
+        match $e {
+            Ok(v) => v,
+            Err(e) => {
+                use proc_macro2::Span;
+                use quote::*;
+                let msg = e.to_string();
+                return Into::into(quote_spanned!(Span::call_site() => compile_error!(#msg)));
+            }
+        }
+    };
+}
+
+macro_rules! bail_quote {
+    ($e:expr) => {{
+        use proc_macro2::Span;
+        use quote::*;
+        let msg = $e.to_string();
+        return Into::into(quote_spanned!(Span::call_site() => compile_error!(#msg)));
+    }};
+    ($e:expr, $($args:expr),*) => {{
+        bail_quote!(format!($e, $($args),*))
+    }}
+}
+
+#[derive(Debug, Copy, Clone, PartialEq)]
+enum HandlerMode {
+    Ready,
+    Async,
+    AsyncAwait,
+}
+
+impl std::str::FromStr for HandlerMode {
+    type Err = String;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        match s.trim() {
+            "" | "ready" => Ok(HandlerMode::Ready),
+            "async" => Ok(HandlerMode::Async),
+            "await" => Ok(HandlerMode::AsyncAwait),
+            s => Err(format!("invalid mode: `{}'", s)),
+        }
+    }
+}
+
+fn detect_mode(attr: &TokenStream, _item: &syn::ItemFn) -> Result<HandlerMode, String> {
+    attr.to_string().parse()
+}
+
+/// Modifies the signature of a free-standing function to a suitable form for using the handler.
+///
+/// # Examples
+///
+/// ```
+/// # #![feature(proc_macro, use_extern_macros)]
+/// # extern crate tsukuyomi;
+/// # extern crate tsukuyomi_codegen;
+/// # use tsukuyomi_codegen::handler;
+/// #[handler]
+/// fn handler() -> &'static str {
+///     "Hello"
+/// }
+/// ```
+///
+/// ```
+/// # #![feature(proc_macro, use_extern_macros)]
+/// # extern crate tsukuyomi;
+/// # extern crate tsukuyomi_codegen;
+/// # use tsukuyomi_codegen::handler;
+/// # use tsukuyomi::Input;
+/// #[handler]
+/// fn handler(input: &mut Input) -> String {
+///     format!("path = {:?}", input.uri().path())
+/// }
+/// ```
+///
+/// ```
+/// # #![feature(proc_macro, use_extern_macros)]
+/// # extern crate tsukuyomi;
+/// # extern crate tsukuyomi_codegen;
+/// # extern crate futures;
+/// # use tsukuyomi_codegen::handler;
+/// # use tsukuyomi::{Input, Error};
+/// # use futures::Future;
+/// #[handler(async)]
+/// fn handler(input: &mut Input) -> impl Future<Item = String, Error = Error> + Send + 'static {
+///     input.body_mut().read_all().convert_to()
+/// }
+/// ```
+///
+/// ```
+/// # #![feature(proc_macro, use_extern_macros, proc_macro_non_items, generators)]
+/// # extern crate tsukuyomi;
+/// # extern crate tsukuyomi_codegen;
+/// # extern crate futures_await as futures;
+/// # use tsukuyomi_codegen::handler;
+/// # use tsukuyomi::Error;
+/// #[handler(await)]
+/// fn handler() -> Result<&'static str, Error> {
+///     Ok("Hello")
+/// }
+/// ```
+#[proc_macro_attribute]
+pub fn handler(attr: TokenStream, item: TokenStream) -> TokenStream {
+    let item: syn::ItemFn = try_quote!(syn::parse(item));
+
+    // FIXME: detect the keyword `async`
+    let mode = try_quote!(detect_mode(&attr, &item));
+
+    let num_args = item.decl.inputs.iter().count();
+    if num_args > 1 {
+        bail_quote!("Too many arguments");
+    }
+    if mode == HandlerMode::AsyncAwait && num_args != 0 {
+        bail_quote!("The number of arguments in #[async] handler must be zero.");
+    }
+
+    let mut inner = item.clone();
+    inner.ident = syn::Ident::new("inner", inner.ident.span());
+    if mode == HandlerMode::AsyncAwait {
+        inner.attrs.push(parse_quote!(#[async]));
+    }
+
+    let mut new_item = item.clone();
+    let input_ident: syn::Ident = if num_args == 0 && mode != HandlerMode::Ready {
+        syn::Ident::new("_input", Span::call_site())
+    } else {
+        syn::Ident::new("input", Span::call_site())
+    };
+    new_item.decl.inputs = Some(syn::punctuated::Pair::End(parse_quote!(
+        #input_ident: &mut ::tsukuyomi::input::Input
+    ))).into_iter()
+        .collect();
+    match new_item.decl.output {
+        syn::ReturnType::Default => bail_quote!("unimplemented"),
+        syn::ReturnType::Type(_, ref mut ty) => {
+            *ty = Box::new(parse_quote!(::tsukuyomi::handler::Handle));
+        }
+    }
+    new_item.block = {
+        let call: syn::Expr = match num_args {
+            0 => parse_quote!(inner()),
+            1 => parse_quote!(inner(input)),
+            _ => unreachable!(),
+        };
+
+        let body: syn::Expr = match mode {
+            HandlerMode::Ready => parse_quote!({
+                ::tsukuyomi::handler::Handle::ready(
+                    ::tsukuyomi::output::Responder::respond_to(#call, input)
+                )
+            }),
+            HandlerMode::Async | HandlerMode::AsyncAwait => parse_quote!({
+                ::tsukuyomi::handler::Handle::async_responder(#call)
+            }),
+        };
+
+        let prelude: Option<syn::Stmt> = if mode == HandlerMode::AsyncAwait {
+            Some(parse_quote!(use futures::prelude::async;))
+        } else {
+            None
+        };
+
+        Box::new(parse_quote!({
+            #prelude
+            #inner
+            #body
+        }))
+    };
+
+    quote!(#new_item).into()
+}
diff --git a/tsukuyomi-codegen/tests/smokes.rs b/tsukuyomi-codegen/tests/smokes.rs
new file mode 100644
index 000000000..f2cc70473
--- /dev/null
+++ b/tsukuyomi-codegen/tests/smokes.rs
@@ -0,0 +1,56 @@
+#![feature(proc_macro, proc_macro_non_items, generators)]
+
+extern crate futures_await as futures;
+extern crate tsukuyomi;
+extern crate tsukuyomi_codegen;
+
+use futures::future;
+use futures::prelude::{async, await, Future};
+use tsukuyomi::{Error, Handler, Input};
+use tsukuyomi_codegen::handler;
+
+#[allow(dead_code)]
+fn ready_without_input() {
+    #[handler]
+    fn handler() -> &'static str {
+        "Hello"
+    }
+    let _ = Handler::new(handler);
+}
+
+#[allow(dead_code)]
+fn ready_with_input() {
+    #[handler]
+    fn handler(_: &mut Input) -> &'static str {
+        "Hello"
+    }
+    let _ = Handler::new(handler);
+}
+
+#[allow(dead_code)]
+fn async_without_input() {
+    #[handler(async)]
+    fn handler() -> impl Future<Item = &'static str, Error = Error> + Send + 'static {
+        future::ok("Hello")
+    }
+    let _ = Handler::new(handler);
+}
+
+#[allow(dead_code)]
+fn async_with_input() {
+    #[handler(async)]
+    fn handler(_: &mut Input) -> impl Future<Item = &'static str, Error = Error> + Send + 'static {
+        future::ok("Hello")
+    }
+    let _ = Handler::new(handler);
+}
+
+#[allow(dead_code)]
+fn async_with_await() {
+    #[handler(await)]
+    fn handler() -> Result<&'static str, Error> {
+        await!(future::ok::<(), Error>(()))?;
+        Ok("Hello")
+    }
+    let _ = Handler::new(handler);
+}