diff --git a/runtime/doc/builtin.txt b/runtime/doc/builtin.txt
index 635b7b2..9c3d7a9 100644
--- a/runtime/doc/builtin.txt
+++ b/runtime/doc/builtin.txt
@@ -309,6 +309,7 @@
 hlset({list})			Number	set highlight group attributes
 hostname()			String	name of the machine Vim is running on
 iconv({expr}, {from}, {to})	String	convert encoding of {expr}
+id({item})			String	get address of item as a string
 indent({lnum})			Number	indent of line {lnum}
 index({object}, {expr} [, {start} [, {ic}]])
 				Number	index in {object} where {expr} appears
@@ -5618,6 +5619,34 @@
 		Return type: |String|
 
 
+id({item})							    *id()*
+		The result is a unique String associated with the {item} and
+		not with the {item}'s contents. It is only valid while the
+		{item} exists and is referenced. It is valid only in the
+		instance of vim that produces the result. The whole idea is
+		that `id({item})` does not change if the contents of {item}
+		changes. This is useful as a `key` for creating an identity
+		dictionary, rather than one based on equals.
+
+		This operation does not reference {item} and there is no
+		function to convert the `id` to the {item}. It may be useful to
+		have a map of `id` to {item}. The following >
+		    var referenceMap: dict<any>
+		    var id = item->id()
+		    referenceMap[id] = item
+<		prevents {item} from being garbage collected and provides a
+		way to get the {item} from the `id`.
+
+		{item} may be a List, Dictionary, Object, Job, Channel or
+		Blob. If the item is not a permitted type, or it is a null
+		value, then an empty String is returned.
+
+		Can also be used as a |method|: >
+			GetItem()->id()
+<
+		Return type: |String|
+
+
 indent({lnum})							*indent()*
 		The result is a Number, which is indent of line {lnum} in the
 		current buffer.  The indent is counted in spaces, the value
diff --git a/runtime/doc/tags b/runtime/doc/tags
index be71710..adbc145 100644
--- a/runtime/doc/tags
+++ b/runtime/doc/tags
@@ -8302,6 +8302,7 @@
 iconize	starting.txt	/*iconize*
 iconv()	builtin.txt	/*iconv()*
 iconv-dynamic	mbyte.txt	/*iconv-dynamic*
+id()	builtin.txt	/*id()*
 ident-search	tips.txt	/*ident-search*
 idl-syntax	syntax.txt	/*idl-syntax*
 idl.vim	syntax.txt	/*idl.vim*
diff --git a/runtime/doc/usr_41.txt b/runtime/doc/usr_41.txt
index 922e80a..765eab5 100644
--- a/runtime/doc/usr_41.txt
+++ b/runtime/doc/usr_41.txt
@@ -1408,6 +1408,8 @@
 
 	wordcount()		get byte/word/char count of buffer
 
+	id()			get unique string for item to use as a key
+
 	luaeval()		evaluate |Lua| expression
 	mzeval()		evaluate |MzScheme| expression
 	perleval()		evaluate Perl expression (|+perl|)
diff --git a/runtime/doc/version9.txt b/runtime/doc/version9.txt
index 43de269..86ec020 100644
--- a/runtime/doc/version9.txt
+++ b/runtime/doc/version9.txt
@@ -1,4 +1,4 @@
-*version9.txt*  For Vim version 9.1.  Last change: 2024 Jul 08
+*version9.txt*  For Vim version 9.1.  Last change: 2024 Jul 09
 
 
 		  VIM REFERENCE MANUAL    by Bram Moolenaar
@@ -41593,6 +41593,8 @@
 |foreach()|		apply function to List items
 |getregion()|		get a region of text from a buffer
 |getregionpos()|	get a list of positions for a region
+|id()|			get unique identifier for a Dict, List, Object,
+			Channel or Blob variable
 |matchbufline()|	all the matches of a pattern in a buffer
 |matchstrlist()|	all the matches of a pattern in a List of strings
 |popup_setbuf()|	switch to a different buffer in a popup
diff --git a/src/evalfunc.c b/src/evalfunc.c
index 5e3122d..370b26b 100644
--- a/src/evalfunc.c
+++ b/src/evalfunc.c
@@ -82,6 +82,7 @@
 static void f_hlID(typval_T *argvars, typval_T *rettv);
 static void f_hlexists(typval_T *argvars, typval_T *rettv);
 static void f_hostname(typval_T *argvars, typval_T *rettv);
+static void f_id(typval_T *argvars, typval_T *rettv);
 static void f_index(typval_T *argvars, typval_T *rettv);
 static void f_indexof(typval_T *argvars, typval_T *rettv);
 static void f_input(typval_T *argvars, typval_T *rettv);
@@ -2207,6 +2208,8 @@
 			ret_string,	    f_hostname},
     {"iconv",		3, 3, FEARG_1,	    arg3_string,
 			ret_string,	    f_iconv},
+    {"id",		1, 1, FEARG_1,	    NULL,
+			ret_string,	    f_id},
     {"indent",		1, 1, FEARG_1,	    arg1_lnum,
 			ret_number,	    f_indent},
     {"index",		2, 4, FEARG_1,	    arg24_index,
@@ -7517,6 +7520,40 @@
 }
 
 /*
+ * "id()" function
+ * Identity. Return address of item as a hex string, %p format.
+ * Currently only valid for object/container types.
+ * Return empty string if not an object.
+ */
+    void
+f_id(typval_T *argvars, typval_T *rettv)
+{
+    char_u	numbuf[NUMBUFLEN];
+
+    switch (argvars[0].v_type)
+    {
+	case VAR_LIST:
+	case VAR_DICT:
+	case VAR_OBJECT:
+	case VAR_JOB:
+	case VAR_CHANNEL:
+	case VAR_BLOB:
+	    // Assume pointer value in typval_T vval union at common location.
+	    if (argvars[0].vval.v_object != NULL)
+		vim_snprintf((char*)numbuf, sizeof(numbuf), "%p",
+					    (void *)argvars[0].vval.v_object);
+	    else
+		numbuf[0] = NUL;
+	    break;
+	default:
+	    numbuf[0] = NUL;
+    }
+
+    rettv->v_type = VAR_STRING;
+    rettv->vval.v_string = vim_strsave(numbuf);
+}
+
+/*
  * "index()" function
  */
     static void
diff --git a/src/testdir/test_listdict.vim b/src/testdir/test_listdict.vim
index 0a4f88c..48217cf 100644
--- a/src/testdir/test_listdict.vim
+++ b/src/testdir/test_listdict.vim
@@ -1619,4 +1619,34 @@
   call v9.CheckLegacyAndVim9Success(lines)
 endfunc
 
+" Test for using id()
+def Test_id_with_dict()
+  # demonstate a way that "id(item)" differs from "string(item)"
+  var d1 = {one: 1}
+  var d2 = {one: 1}
+  var d3 = {one: 1}
+  var idDict: dict<any>
+  idDict[id(d1)] = d1
+  idDict[id(d2)] = d2
+  idDict[id(d3)] = d3
+  assert_equal(3, idDict->len())
+
+  var stringDict: dict<any>
+  stringDict[string(d1)] = d1
+  stringDict[string(d2)] = d2
+  stringDict[string(d3)] = d3
+  assert_equal(1, stringDict->len())
+
+  assert_equal('', id(3))
+
+  assert_equal('', id(null))
+  assert_equal('', id(null_blob))
+  assert_equal('', id(null_dict))
+  assert_equal('', id(null_function))
+  assert_equal('', id(null_list))
+  assert_equal('', id(null_partial))
+  assert_equal('', id(null_string))
+  assert_equal('', id(null_channel))
+  assert_equal('', id(null_job))
+enddef
 " vim: shiftwidth=2 sts=2 expandtab
diff --git a/src/version.c b/src/version.c
index ce6b8d6..1f334ca 100644
--- a/src/version.c
+++ b/src/version.c
@@ -705,6 +705,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    548,
+/**/
     547,
 /**/
     546,