diff --git a/src/eval.c b/src/eval.c
index 0b589fd..5025a52 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -434,7 +434,6 @@
 static int tv_equal(typval_T *tv1, typval_T *tv2, int ic, int recursive);
 static long list_find_nr(list_T *l, long idx, int *errorp);
 static long list_idx_of_item(list_T *l, listitem_T *item);
-static int list_append_number(list_T *l, varnumber_T n);
 static int list_extend(list_T	*l1, list_T *l2, listitem_T *bef);
 static int list_concat(list_T *l1, list_T *l2, typval_T *tv);
 static list_T *list_copy(list_T *orig, int deep, int copyID);
@@ -808,6 +807,10 @@
 static void f_virtcol(typval_T *argvars, typval_T *rettv);
 static void f_visualmode(typval_T *argvars, typval_T *rettv);
 static void f_wildmenumode(typval_T *argvars, typval_T *rettv);
+static void f_win_getid(typval_T *argvars, typval_T *rettv);
+static void f_win_gotoid(typval_T *argvars, typval_T *rettv);
+static void f_win_id2tabwin(typval_T *argvars, typval_T *rettv);
+static void f_win_id2win(typval_T *argvars, typval_T *rettv);
 static void f_winbufnr(typval_T *argvars, typval_T *rettv);
 static void f_wincol(typval_T *argvars, typval_T *rettv);
 static void f_winheight(typval_T *argvars, typval_T *rettv);
@@ -6469,7 +6472,7 @@
  * Append "n" to list "l".
  * Returns FAIL when out of memory.
  */
-    static int
+    int
 list_append_number(list_T *l, varnumber_T n)
 {
     listitem_T	*li;
@@ -8385,6 +8388,10 @@
     {"virtcol",		1, 1, f_virtcol},
     {"visualmode",	0, 1, f_visualmode},
     {"wildmenumode",	0, 0, f_wildmenumode},
+    {"win_getid",	0, 2, f_win_getid},
+    {"win_gotoid",	1, 1, f_win_gotoid},
+    {"win_id2tabwin",	1, 1, f_win_id2tabwin},
+    {"win_id2win",	1, 1, f_win_id2win},
     {"winbufnr",	1, 1, f_winbufnr},
     {"wincol",		0, 0, f_wincol},
     {"winheight",	1, 1, f_winheight},
@@ -12662,6 +12669,43 @@
 }
 
 /*
+ * "win_getid()" function
+ */
+    static void
+f_win_getid(typval_T *argvars, typval_T *rettv)
+{
+    rettv->vval.v_number = win_getid(argvars);
+}
+
+/*
+ * "win_gotoid()" function
+ */
+    static void
+f_win_gotoid(typval_T *argvars, typval_T *rettv)
+{
+    rettv->vval.v_number = win_gotoid(argvars);
+}
+
+/*
+ * "win_id2tabwin()" function
+ */
+    static void
+f_win_id2tabwin(typval_T *argvars, typval_T *rettv)
+{
+    if (rettv_list_alloc(rettv) != FAIL)
+	win_id2tabwin(argvars, rettv->vval.v_list);
+}
+
+/*
+ * "win_id2win()" function
+ */
+    static void
+f_win_id2win(typval_T *argvars, typval_T *rettv)
+{
+    rettv->vval.v_number = win_id2win(argvars);
+}
+
+/*
  * "getwinposy()" function
  */
     static void
diff --git a/src/proto/eval.pro b/src/proto/eval.pro
index f5e0d19..7035f26 100644
--- a/src/proto/eval.pro
+++ b/src/proto/eval.pro
@@ -59,6 +59,7 @@
 int list_append_tv(list_T *l, typval_T *tv);
 int list_append_dict(list_T *list, dict_T *dict);
 int list_append_string(list_T *l, char_u *str, int len);
+int list_append_number(list_T *l, varnumber_T n);
 int list_insert_tv(list_T *l, typval_T *tv, listitem_T *item);
 void list_insert(list_T *l, listitem_T *ni, listitem_T *item);
 void vimlist_remove(list_T *l, listitem_T *item, listitem_T *item2);
diff --git a/src/proto/window.pro b/src/proto/window.pro
index 613fe21..3c511e3 100644
--- a/src/proto/window.pro
+++ b/src/proto/window.pro
@@ -83,4 +83,8 @@
 matchitem_T *get_match(win_T *wp, int id);
 int get_win_number(win_T *wp, win_T *first_win);
 int get_tab_number(tabpage_T *tp);
+int win_getid(typval_T *argvars);
+int win_gotoid(typval_T *argvars);
+void win_id2tabwin(typval_T *argvars, list_T *list);
+int win_id2win(typval_T *argvars);
 /* vim: set ft=c : */
diff --git a/src/structs.h b/src/structs.h
index 6bf2126..4aa7415 100644
--- a/src/structs.h
+++ b/src/structs.h
@@ -2273,6 +2273,8 @@
  */
 struct window_S
 {
+    int		w_id;		    /* unique window ID */
+
     buf_T	*w_buffer;	    /* buffer we are a window into (used
 				       often, keep it the first item!) */
 
diff --git a/src/testdir/Make_all.mak b/src/testdir/Make_all.mak
index 5ad1718..233ca12 100644
--- a/src/testdir/Make_all.mak
+++ b/src/testdir/Make_all.mak
@@ -186,6 +186,7 @@
 	    test_viminfo.res \
 	    test_viml.res \
 	    test_visual.res \
+	    test_window_id.res \
 	    test_alot.res
 
 
diff --git a/src/testdir/test_window_id.vim b/src/testdir/test_window_id.vim
new file mode 100644
index 0000000..b9e9f45
--- /dev/null
+++ b/src/testdir/test_window_id.vim
@@ -0,0 +1,71 @@
+" Test using the window ID.
+
+func Test_win_getid()
+  edit one
+  let id1 = win_getid()
+  split two
+  let id2 = win_getid()
+  split three
+  let id3 = win_getid()
+  tabnew
+  edit four
+  let id4 = win_getid()
+  split five
+  let id5 = win_getid()
+  tabnext
+
+  wincmd w
+  call assert_equal("two", expand("%"))
+  call assert_equal(id2, win_getid())
+  let nr2 = winnr()
+  wincmd w
+  call assert_equal("one", expand("%"))
+  call assert_equal(id1, win_getid())
+  let nr1 = winnr()
+  wincmd w
+  call assert_equal("three", expand("%"))
+  call assert_equal(id3, win_getid())
+  let nr3 = winnr()
+  tabnext
+  call assert_equal("five", expand("%"))
+  call assert_equal(id5, win_getid())
+  let nr5 = winnr()
+  wincmd w
+  call assert_equal("four", expand("%"))
+  call assert_equal(id4, win_getid())
+  let nr4 = winnr()
+  tabnext
+
+  exe nr1 . "wincmd w"
+  call assert_equal(id1, win_getid())
+  exe nr2 . "wincmd w"
+  call assert_equal(id2, win_getid())
+  exe nr3 . "wincmd w"
+  call assert_equal(id3, win_getid())
+  tabnext
+  exe nr4 . "wincmd w"
+  call assert_equal(id4, win_getid())
+  exe nr5 . "wincmd w"
+  call assert_equal(id5, win_getid())
+
+  call win_gotoid(id2)
+  call assert_equal("two", expand("%"))
+  call win_gotoid(id4)
+  call assert_equal("four", expand("%"))
+  call win_gotoid(id1)
+  call assert_equal("one", expand("%"))
+  call win_gotoid(id5)
+  call assert_equal("five", expand("%"))
+
+  call assert_equal(0, win_id2win(9999))
+  call assert_equal(nr5, win_id2win(id5))
+  call assert_equal(0, win_id2win(id1))
+  tabnext
+  call assert_equal(nr1, win_id2win(id1))
+
+  call assert_equal([0, 0], win_id2tabwin(9999))
+  call assert_equal([1, nr2], win_id2tabwin(id2))
+  call assert_equal([2, nr4], win_id2tabwin(id4))
+
+  only!
+endfunc
diff --git a/src/version.c b/src/version.c
index 9c15aaf..bed7a46 100644
--- a/src/version.c
+++ b/src/version.c
@@ -744,6 +744,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1557,
+/**/
     1556,
 /**/
     1555,
diff --git a/src/window.c b/src/window.c
index 7dfbe5a..b6111bd 100644
--- a/src/window.c
+++ b/src/window.c
@@ -4541,6 +4541,8 @@
 }
 #endif
 
+static int last_win_id = 0;
+
 /*
  * Allocate a window structure and link it in the window list when "hidden" is
  * FALSE.
@@ -4563,6 +4565,8 @@
 	return NULL;
     }
 
+    new_wp->w_id = ++last_win_id;
+
 #ifdef FEAT_EVAL
     /* init w: variables */
     new_wp->w_vars = dict_alloc();
@@ -7198,3 +7202,99 @@
 }
 #endif
 
+#if defined(FEAT_EVAL) || defined(PROTO)
+    int
+win_getid(typval_T *argvars)
+{
+    int	    winnr;
+    win_T   *wp;
+
+    if (argvars[0].v_type == VAR_UNKNOWN)
+	return curwin->w_id;
+    winnr = get_tv_number(&argvars[0]);
+    if (winnr > 0)
+    {
+	if (argvars[1].v_type == VAR_UNKNOWN)
+	    wp = firstwin;
+	else
+	{
+	    tabpage_T	*tp;
+	    int		tabnr = get_tv_number(&argvars[1]);
+
+	    for (tp = first_tabpage; tp != NULL; tp = tp->tp_next)
+		if (--tabnr == 0)
+		    break;
+	    if (tp == NULL)
+		return -1;
+	    wp = tp->tp_firstwin;
+	}
+	for ( ; wp != NULL; wp = wp->w_next)
+	    if (--winnr == 0)
+		return wp->w_id;
+    }
+    return 0;
+}
+
+    int
+win_gotoid(typval_T *argvars)
+{
+    win_T	*wp;
+    tabpage_T   *tp;
+    int		id = get_tv_number(&argvars[0]);
+
+    for (tp = first_tabpage; tp != NULL; tp = tp->tp_next)
+	for (wp = tp == curtab ? firstwin : tp->tp_firstwin;
+						  wp != NULL; wp = wp->w_next)
+	    if (wp->w_id == id)
+	    {
+		goto_tabpage_win(tp, wp);
+		return 1;
+	    }
+    return 0;
+}
+
+    void
+win_id2tabwin(typval_T *argvars, list_T *list)
+{
+    win_T	*wp;
+    tabpage_T   *tp;
+    int		winnr = 1;
+    int		tabnr = 1;
+    int		id = get_tv_number(&argvars[0]);
+
+    for (tp = first_tabpage; tp != NULL; tp = tp->tp_next)
+    {
+	for (wp = tp == curtab ? firstwin : tp->tp_firstwin;
+						  wp != NULL; wp = wp->w_next)
+	{
+	    if (wp->w_id == id)
+	    {
+		list_append_number(list, tabnr);
+		list_append_number(list, winnr);
+		return;
+	    }
+	    ++winnr;
+	}
+	++tabnr;
+	winnr = 1;
+    }
+    list_append_number(list, 0);
+    list_append_number(list, 0);
+}
+
+    int
+win_id2win(typval_T *argvars)
+{
+    win_T   *wp;
+    int	    nr = 1;
+    int	    id = get_tv_number(&argvars[0]);
+
+    for (wp = firstwin; wp != NULL; wp = wp->w_next)
+    {
+	if (wp->w_id == id)
+	    return nr;
+	++nr;
+    }
+    return 0;
+}
+#endif