diff --git a/Doc/library/gzip.rst b/Doc/library/gzip.rst
index ccf9bbb28de14f..d6f72c1610c560 100644
--- a/Doc/library/gzip.rst
+++ b/Doc/library/gzip.rst
@@ -253,6 +253,10 @@ Example of how to GZIP compress a binary string::
       The basic data compression module needed to support the :program:`gzip` file
       format.
 
+   In case gzip (de)compression is a bottleneck, the `python-isal`_
+   package speeds up (de)compression with a mostly compatible API.
+
+   .. _python-isal: https://github.com/pycompression/python-isal
 
 .. program:: gzip
 
diff --git a/Doc/library/zlib.rst b/Doc/library/zlib.rst
index 965b82a3daffb9..4f0eac0a9d51f8 100644
--- a/Doc/library/zlib.rst
+++ b/Doc/library/zlib.rst
@@ -341,3 +341,8 @@ the following constants:
    http://www.zlib.net/manual.html
       The zlib manual explains  the semantics and usage of the library's many
       functions.
+
+   In case gzip (de)compression is a bottleneck, the `python-isal`_
+   package speeds up (de)compression with a mostly compatible API.
+
+   .. _python-isal: https://github.com/pycompression/python-isal