diff --git a/configure.ac b/configure.ac
index 5818e032..b6e43164 100644
--- a/configure.ac
+++ b/configure.ac
@@ -54,14 +54,14 @@ AS_IF([test "x$with_gssapi" != xno],
 
 AC_ARG_WITH([gtk],
   [AS_HELP_STRING([--with-gtk=VER],
-                  [specify GTK version to use (`1' or `2')])
+                  [specify GTK version to use (`1', `2' or `3')])
 AS_HELP_STRING([--without-gtk],
                   [do not use GTK (build command-line tools only)])],
   [gtk_version_desired="$withval"],
   [gtk_version_desired="any"])
 
 case "$gtk_version_desired" in
-  1 | 2 | any | no) ;;
+  1 | 2 | 3 | any | no) ;;
   yes) gtk_version_desired="any" ;;
   *) AC_ERROR([Invalid GTK version specified])
 esac
@@ -70,8 +70,15 @@ AC_CHECK_HEADERS([utmpx.h sys/select.h],,,[
 #include <sys/types.h>
 #include <utmp.h>])
 
-# Look for both GTK 2 and GTK 1, in descending order of preference. If
-# we can't find either, have the makefile only build the CLI programs.
+# Look for GTK 2, GTK 3 and GTK 1, in descending order of preference.
+#
+# (I like GTK 2 for its faster support for X server-side fonts due to
+# not being required to do all its drawing via Cairo; GTK 3 is
+# tolerable if GTK 2 can't be had, and GTK 1 is an extreme fallback
+# for platforms - of which I've heard of at least one - to which
+# nothing newer has ever been ported.)
+#
+# If we can't find any, have the makefile only build the CLI programs.
 
 gtk=none
 
@@ -83,6 +90,17 @@ case "$gtk_version_desired:$gtk" in
     ;;
 esac
 
+case "$gtk_version_desired:$gtk" in
+  3:none | any:none)
+    ifdef([AM_PATH_GTK_3_0],[
+    AM_PATH_GTK_3_0([3.0.0], [
+    gtk=3
+    GTK_CFLAGS="$GTK_CFLAGS -Wno-deprecated-declarations"
+    ], [])
+    ],[AC_WARNING([generating configure script without GTK 3 autodetection])])
+    ;;
+esac
+
 case "$gtk_version_desired:$gtk" in
   1:none | any:none)
     ifdef([AM_PATH_GTK],[
@@ -101,7 +119,7 @@ esac
 
 AM_CONDITIONAL(HAVE_GTK, [test "$gtk" != "none"])
 
-if test "$gtk" = "2"; then
+if test "$gtk" = "2" -o "$gtk" = "3"; then
   ac_save_CFLAGS="$CFLAGS"
   ac_save_LIBS="$LIBS"
   CFLAGS="$CFLAGS $GTK_CFLAGS"
@@ -174,11 +192,18 @@ psftp will be built.
 EOF
 elif test "$gtk" = "none"; then cat <<EOF
 
-'configure' was unable to find either the GTK 1 or GTK 2 libraries on
+'configure' was unable to find any version of the GTK libraries on
 your system. Therefore, PuTTY itself and the other GUI utilities will
 not be built by the generated Makefile: only the command-line tools
 such as puttygen, plink and psftp will be built.
 
+EOF
+elif test "$gtk" = "3"; then cat <<EOF
+
+PuTTY will be built with GTK 3. Be aware that the GTK 3 support in
+this codebase is UNFINISHED AND EXPERIMENTAL! Many deprecated
+functions are used, and there are known layout bugs.
+
 EOF
 fi