diff --git a/README.rst b/README.rst
index 002377a7..f18c55b4 100644
--- a/README.rst
+++ b/README.rst
@@ -11,8 +11,6 @@ HTTP/2.
 
 An HPACK encoder and decoder are available as a public API.
 
-An experimental high level C++ library is also available.
-
 We have Python bindings of this library, but we do not have full
 code coverage yet.
 
@@ -106,7 +104,8 @@ To mitigate heap fragmentation in long running server programs
      Alpine Linux currently does not support malloc replacement
      due to musl limitations. See details in issue `#762 <https://github.com/nghttp2/nghttp2/issues/762>`_.
 
-libnghttp2_asio C++ library requires the following packages:
+libnghttp2_asio C++ library (deprecated) requires the following
+packages:
 
 * libboost-dev >= 1.54.0
 * libboost-thread-dev >= 1.54.0
@@ -1434,6 +1433,8 @@ corresponding header set was processed.  The format is the same as
 libnghttp2_asio: High level HTTP/2 C++ library
 ----------------------------------------------
 
+libnghttp2_asio has been deprecated.
+
 libnghttp2_asio is C++ library built on top of libnghttp2 and provides
 high level abstraction API to build HTTP/2 applications.  It depends
 on the Boost::ASIO library and OpenSSL.  Currently libnghttp2_asio
diff --git a/doc/sources/libnghttp2_asio.rst b/doc/sources/libnghttp2_asio.rst
index 2f348e77..8e9fd04d 100644
--- a/doc/sources/libnghttp2_asio.rst
+++ b/doc/sources/libnghttp2_asio.rst
@@ -1,6 +1,11 @@
 libnghttp2_asio: High level HTTP/2 C++ library
 ==============================================
 
+.. warning::
+
+    libnghttp2_asio has been deprecated due to maintenance issue.  It
+    will not get any updates.  It will be removed at the end of 2022.
+
 libnghttp2_asio is C++ library built on top of libnghttp2 and provides
 high level abstraction API to build HTTP/2 applications.  It depends
 on Boost::ASIO library and OpenSSL.  Currently libnghttp2_asio