diff --git a/mercurial/help/config.txt b/mercurial/help/config.txt
--- a/mercurial/help/config.txt
+++ b/mercurial/help/config.txt
@@ -1557,6 +1557,21 @@ Controls generic server settings.
     repositories to the exchange format required by the bundle1 data
     format can consume a lot of CPU.
 
+``zliblevel``
+    Integer between ``-1`` and ``9`` that controls the zlib compression level
+    for wire protocol commands that send zlib compressed output (notably the
+    commands that send repository history data).
+
+    The default (``-1``) uses the default zlib compression level, which is
+    likely equivalent to ``6``. ``0`` means no compression. ``9`` means
+    maximum compression.
+
+    Setting this option allows server operators to make trade-offs between
+    bandwidth and CPU used. Lowering the compression lowers CPU utilization
+    but sends more bytes to clients.
+
+    This option only impacts the HTTP server.
+
 ``smtp``
 --------
 
diff --git a/mercurial/hgweb/protocol.py b/mercurial/hgweb/protocol.py
--- a/mercurial/hgweb/protocol.py
+++ b/mercurial/hgweb/protocol.py
@@ -74,7 +74,7 @@ class webproto(wireproto.abstractserverp
         self.ui.ferr, self.ui.fout = self.oldio
         return val
     def groupchunks(self, cg):
-        z = zlib.compressobj()
+        z = zlib.compressobj(self.ui.configint('server', 'zliblevel', -1))
         while True:
             chunk = cg.read(4096)
             if not chunk: