diff --git a/pkgs/applications/networking/browsers/icecat-4/default.nix b/pkgs/applications/networking/browsers/icecat-4/default.nix
new file mode 100644
index 00000000000..a63584fda28
--- /dev/null
+++ b/pkgs/applications/networking/browsers/icecat-4/default.nix
@@ -0,0 +1,118 @@
+{ fetchurl, stdenv, xz, pkgconfig, gtk, pango, perl, python, ply, zip, libIDL
+, libjpeg, libpng, zlib, cairo, dbus, dbus_glib, bzip2, xlibs, alsaLib
+, libnotify, gnomevfs, libgnomeui
+, freetype, fontconfig, wirelesstools ? null, pixman
+, application ? "browser" }:
+
+# Build the WiFi stuff on Linux-based systems.
+# FIXME: Disable for now until it can actually be built:
+# http://thread.gmane.org/gmane.comp.gnu.gnuzilla/1376 .
+#assert stdenv.isLinux -> (wirelesstools != null);
+
+let version = "3.6.15"; in
+stdenv.mkDerivation {
+  name = "icecat-${version}";
+
+  src = fetchurl {
+    url = "mirror://gnu/gnuzilla/${version}/icecat-${version}.tar.xz";
+    sha256 = "1px018bd81c81a4hbz0qgf89pkshkbhg4abwq1d26dwy8128cxwg";
+  };
+
+  buildInputs =
+    [ xz libgnomeui libnotify gnomevfs alsaLib
+      pkgconfig gtk perl zip libIDL libjpeg libpng zlib cairo bzip2 pixman
+      python ply dbus dbus_glib pango freetype fontconfig
+      xlibs.libXi xlibs.libX11 xlibs.libXrender xlibs.libXft xlibs.libXt
+    ]
+    ++ (stdenv.lib.optional false /* stdenv.isLinux */ wirelesstools);
+
+  patches = [
+    ./skip-gre-registration.patch ./rpath-link.patch
+  ];
+
+  configureFlags =
+    [ "--enable-application=${application}"
+      "--enable-libxul"
+      "--disable-javaxpcom"
+
+      "--enable-optimize"
+      "--disable-debug"
+      "--enable-strip"
+      "--with-system-jpeg"
+      "--with-system-zlib"
+      "--with-system-bz2"
+      # "--with-system-png" # <-- "--with-system-png won't work because the system's libpng doesn't have APNG support"
+      "--enable-system-cairo"
+      #"--enable-system-sqlite" # <-- this seems to be discouraged
+      "--disable-crashreporter"
+    ]
+    ++ (stdenv.lib.optional true /* (!stdenv.isLinux) */ "--disable-necko-wifi");
+
+  postInstall = ''
+    export dontPatchELF=1;
+
+    # Strip some more stuff
+    strip -S "$out/lib/"*"/"* || true
+
+    # This fixes starting IceCat when there already is a running
+    # instance.  The `icecat' wrapper script actually expects to be
+    # in the same directory as `run-mozilla.sh', apparently.
+    libDir=$(cd $out/lib && ls -d icecat-[0-9]*)
+    test -n "$libDir"
+
+    if [ -f "$out/bin/icecat" ]
+    then
+        # Fix references to /bin paths in the IceCat shell script.
+        substituteInPlace $out/bin/icecat		\
+            --replace /bin/pwd "$(type -tP pwd)"	\
+            --replace /bin/ls "$(type -tP ls)"
+
+        cd $out/bin
+        mv icecat ../lib/$libDir/
+        ln -s ../lib/$libDir/icecat .
+
+        # Register extensions etc.
+        echo "running \`icecat -register'..."
+        (cd $out/lib/$libDir && LD_LIBRARY_PATH=. ./icecat-bin -register) || false
+    fi
+
+    if [ -f "$out/lib/$libDir/xpidl" ]
+    then
+        # XulRunner's IDL compiler.
+        echo "linking \`xpidl'..."
+        ln -s "$out/lib/$libDir/xpidl" "$out/bin"
+    fi
+
+    # Put the GNU IceCat icon in the right place.
+    ensureDir "$out/lib/$libDir/chrome/icons/default"
+    ln -s ../../../icons/default.xpm  "$out/lib/$libDir/chrome/icons/default/"
+  '';
+
+  enableParallelBuilding = true;
+
+  meta = {
+    description = "GNU IceCat, a free web browser based on Mozilla Firefox";
+
+    longDescription = ''
+      Gnuzilla is the GNU version of the Mozilla suite, and GNU IceCat
+      is the GNU version of the Firefox browser.  Its main advantage
+      is an ethical one: it is entirely free software.  While the
+      source code from the Mozilla project is free software, the
+      binaries that they release include additional non-free software.
+      Also, they distribute and recommend non-free software as
+      plug-ins.  In addition, GNU IceCat includes some privacy
+      protection features.
+    '';
+
+    homepage = http://www.gnu.org/software/gnuzilla/;
+    licenses = [ "GPLv2+" "LGPLv2+" "MPLv1+" ];
+
+    maintainers = [ stdenv.lib.maintainers.ludo ];
+    platforms = stdenv.lib.platforms.gnu;
+  };
+
+  passthru = {
+    inherit gtk version;
+    isFirefox3Like = true;
+  };
+}
diff --git a/pkgs/applications/networking/browsers/icecat-4/rpath-link.patch b/pkgs/applications/networking/browsers/icecat-4/rpath-link.patch
new file mode 100644
index 00000000000..d50784f13ee
--- /dev/null
+++ b/pkgs/applications/networking/browsers/icecat-4/rpath-link.patch
@@ -0,0 +1,14 @@
+Without this patch, IceCat ends up linking with
+`-Wl,-rpath-link=/bin -Wl-,-rpath-link=/lib'.
+
+--- icecat-3.5/js/src/configure	2009-07-04 18:03:01.000000000 +0200
++++ icecat-3.5/js/src/configure	2009-07-13 18:34:30.000000000 +0200
+@@ -4775,7 +4775,6 @@ HOST_AR='$(AR)'
+ HOST_AR_FLAGS='$(AR_FLAGS)'
+ 
+ MOZ_JS_LIBS='-L$(libdir) -lmozjs'
+-MOZ_FIX_LINK_PATHS='-Wl,-rpath-link,$(LIBXUL_DIST)/bin -Wl,-rpath-link,$(PREFIX)/lib'
+ 
+ MOZ_COMPONENT_NSPR_LIBS='-L$(LIBXUL_DIST)/bin $(NSPR_LIBS)'
+ MOZ_XPCOM_OBSOLETE_LIBS='-L$(LIBXUL_DIST)/lib -lxpcom_compat'
+
diff --git a/pkgs/applications/networking/browsers/icecat-4/skip-gre-registration.patch b/pkgs/applications/networking/browsers/icecat-4/skip-gre-registration.patch
new file mode 100644
index 00000000000..d1fb4e3f30a
--- /dev/null
+++ b/pkgs/applications/networking/browsers/icecat-4/skip-gre-registration.patch
@@ -0,0 +1,12 @@
+Skip "GRE" registration since that assumes write access to `/etc'.
+
+--- icecat-3.0.1-g1/xulrunner/installer/Makefile.in	2008-07-27 12:52:16.000000000 +0200
++++ icecat-3.0.1-g1/xulrunner/installer/Makefile.in	2008-09-08 17:19:17.000000000 +0200
+@@ -71,6 +71,7 @@ $(MOZILLA_VERSION).system.conf: $(topsrc
+ 	printf "[%s]\nGRE_PATH=%s\nxulrunner=true\nabi=%s" \
+ 	  $(MOZILLA_VERSION) $(installdir) $(TARGET_XPCOM_ABI)> $@
+ 
++SKIP_GRE_REGISTRATION = yes
+ ifndef SKIP_GRE_REGISTRATION
+ # to register xulrunner per-user, override this with $HOME/.gre.d
+ regdir = /etc/gre.d