diff --git a/src/auto/configure b/src/auto/configure
index 4c3ff32..f642a0b 100755
--- a/src/auto/configure
+++ b/src/auto/configure
@@ -12618,7 +12618,7 @@
 	getpwent getpwnam getpwuid getrlimit gettimeofday localtime_r lstat \
 	memset mkdtemp nanosleep opendir putenv qsort readlink select setenv \
 	getpgid setpgid setsid sigaltstack sigstack sigset sigsetjmp sigaction \
-	sigprocmask sigvec strcasecmp strerror strftime stricmp strncasecmp \
+	sigprocmask sigvec strcasecmp strcoll strerror strftime stricmp strncasecmp \
 	strnicmp strpbrk strptime strtol tgetent towlower towupper iswupper \
 	tzset usleep utime utimes mblen ftruncate unsetenv posix_openpt
 do :
diff --git a/src/cmdexpand.c b/src/cmdexpand.c
index b0ea057..9508d66 100644
--- a/src/cmdexpand.c
+++ b/src/cmdexpand.c
@@ -1728,7 +1728,8 @@
 	    {
 		if ( STRNCMP(arg, "messages", p - arg) == 0
 		  || STRNCMP(arg, "ctype", p - arg) == 0
-		  || STRNCMP(arg, "time", p - arg) == 0)
+		  || STRNCMP(arg, "time", p - arg) == 0
+		  || STRNCMP(arg, "collate", p - arg) == 0)
 		{
 		    xp->xp_context = EXPAND_LOCALES;
 		    xp->xp_pattern = skipwhite(p);
diff --git a/src/config.h.in b/src/config.h.in
index 7055b6f..b114480 100644
--- a/src/config.h.in
+++ b/src/config.h.in
@@ -198,6 +198,7 @@
 #undef HAVE_SIGVEC
 #undef HAVE_SMACK
 #undef HAVE_STRCASECMP
+#undef HAVE_STRCOLL
 #undef HAVE_STRERROR
 #undef HAVE_STRFTIME
 #undef HAVE_STRICMP
diff --git a/src/configure.ac b/src/configure.ac
index dccf3dc..0543918 100644
--- a/src/configure.ac
+++ b/src/configure.ac
@@ -3739,7 +3739,7 @@
 	getpwent getpwnam getpwuid getrlimit gettimeofday localtime_r lstat \
 	memset mkdtemp nanosleep opendir putenv qsort readlink select setenv \
 	getpgid setpgid setsid sigaltstack sigstack sigset sigsetjmp sigaction \
-	sigprocmask sigvec strcasecmp strerror strftime stricmp strncasecmp \
+	sigprocmask sigvec strcasecmp strcoll strerror strftime stricmp strncasecmp \
 	strnicmp strpbrk strptime strtol tgetent towlower towupper iswupper \
 	tzset usleep utime utimes mblen ftruncate unsetenv posix_openpt)
 AC_FUNC_SELECT_ARGTYPES
diff --git a/src/evalfunc.c b/src/evalfunc.c
index fe98636..230962e 100644
--- a/src/evalfunc.c
+++ b/src/evalfunc.c
@@ -769,8 +769,8 @@
 			},
     {"rand",		0, 1, FEARG_1,	  ret_number,	f_rand},
     {"range",		1, 3, FEARG_1,	  ret_list_number, f_range},
-    {"readdir",		1, 2, FEARG_1,	  ret_list_string, f_readdir},
-    {"readdirex",	1, 2, FEARG_1,	  ret_list_dict_any, f_readdirex},
+    {"readdir",		1, 3, FEARG_1,	  ret_list_string, f_readdir},
+    {"readdirex",	1, 3, FEARG_1,	  ret_list_dict_any, f_readdirex},
     {"readfile",	1, 3, FEARG_1,	  ret_any,	f_readfile},
     {"reduce",		2, 3, FEARG_1,	  ret_any,	f_reduce},
     {"reg_executing",	0, 0, 0,	  ret_string,	f_reg_executing},
diff --git a/src/evalvars.c b/src/evalvars.c
index d2c71d2..0a0bbc4 100644
--- a/src/evalvars.c
+++ b/src/evalvars.c
@@ -145,6 +145,7 @@
     {VV_NAME("versionlong",	 VAR_NUMBER), VV_RO},
     {VV_NAME("echospace",	 VAR_NUMBER), VV_RO},
     {VV_NAME("argv",		 VAR_LIST), VV_RO},
+    {VV_NAME("collate",		 VAR_STRING), VV_RO},
 };
 
 // shorthand
diff --git a/src/ex_cmds2.c b/src/ex_cmds2.c
index d83facf..f0b5bfd 100644
--- a/src/ex_cmds2.c
+++ b/src/ex_cmds2.c
@@ -1185,6 +1185,14 @@
     loc = get_locale_val(LC_TIME);
 # endif
     set_vim_var_string(VV_LC_TIME, loc, -1);
+
+# ifdef HAVE_GET_LOCALE_VAL
+    loc = get_locale_val(LC_COLLATE);
+# else
+    // setlocale() not supported: use the default value
+    loc = (char_u *)"C";
+# endif
+    set_vim_var_string(VV_COLLATE, loc, -1);
 }
 #endif
 
@@ -1232,6 +1240,12 @@
 	    name = skipwhite(p);
 	    whatstr = "time ";
 	}
+	else if (STRNICMP(eap->arg, "collate", p - eap->arg) == 0)
+	{
+	    what = LC_COLLATE;
+	    name = skipwhite(p);
+	    whatstr = "collate ";
+	}
     }
 
     if (*name == NUL)
@@ -1274,7 +1288,7 @@
 	    // Reset $LC_ALL, otherwise it would overrule everything.
 	    vim_setenv((char_u *)"LC_ALL", (char_u *)"");
 
-	    if (what != LC_TIME)
+	    if (what != LC_TIME && what != LC_COLLATE)
 	    {
 		// Tell gettext() what to translate to.  It apparently doesn't
 		// use the currently effective locale.  Also do this when
@@ -1309,7 +1323,7 @@
 	    }
 
 # ifdef FEAT_EVAL
-	    // Set v:lang, v:lc_time and v:ctype to the final result.
+	    // Set v:lang, v:lc_time, v:collate and v:ctype to the final result.
 	    set_lang_var();
 # endif
 # ifdef FEAT_TITLE
@@ -1462,11 +1476,13 @@
 	return (char_u *)"ctype";
     if (idx == 2)
 	return (char_u *)"time";
+    if (idx == 3)
+	return (char_u *)"collate";
 
     init_locales();
     if (locales == NULL)
 	return NULL;
-    return locales[idx - 3];
+    return locales[idx - 4];
 }
 
 /*
diff --git a/src/fileio.c b/src/fileio.c
index 7b60529..395e54b 100644
--- a/src/fileio.c
+++ b/src/fileio.c
@@ -35,6 +35,10 @@
 static char_u *check_for_bom(char_u *p, long size, int *lenp, int flags);
 static char *e_auchangedbuf = N_("E812: Autocommands changed buffer or buffer name");
 
+#ifdef FEAT_EVAL
+static int readdirex_sort;
+#endif
+
     void
 filemess(
     buf_T	*buf,
@@ -4645,7 +4649,23 @@
 
     name1 = dict_get_string(*(dict_T**)p1, (char_u*)"name", FALSE);
     name2 = dict_get_string(*(dict_T**)p2, (char_u*)"name", FALSE);
-    return STRCMP(name1, name2);
+    if (readdirex_sort == READDIR_SORT_BYTE)
+	return STRCMP(name1, name2);
+    else if (readdirex_sort == READDIR_SORT_IC)
+	return STRICMP(name1, name2);
+    else
+	return STRCOLL(name1, name2);
+}
+
+    static int
+compare_readdir_item(const void *s1, const void *s2)
+{
+    if (readdirex_sort == READDIR_SORT_BYTE)
+	return STRCMP(*(char **)s1, *(char **)s2);
+    else if (readdirex_sort == READDIR_SORT_IC)
+	return STRICMP(*(char **)s1, *(char **)s2);
+    else
+	return STRCOLL(*(char **)s1, *(char **)s2);
 }
 #endif
 
@@ -4663,7 +4683,8 @@
     char_u	*path,
     int		withattr UNUSED,
     void	*context,
-    int		(*checkitem)(void *context, void *item))
+    int		(*checkitem)(void *context, void *item),
+    int         sort)
 {
     int			failed = FALSE;
     char_u		*p;
@@ -4687,6 +4708,8 @@
 	else \
 	    vim_free(item); \
     } while (0)
+
+    readdirex_sort = READDIR_SORT_BYTE;
 # else
 #  define FREE_ITEM(item)   vim_free(item)
 # endif
@@ -4844,15 +4867,19 @@
 
 # undef FREE_ITEM
 
-    if (!failed && gap->ga_len > 0)
+    if (!failed && gap->ga_len > 0 && sort > READDIR_SORT_NONE)
     {
 # ifdef FEAT_EVAL
+	readdirex_sort = sort;
 	if (withattr)
 	    qsort((void*)gap->ga_data, (size_t)gap->ga_len, sizeof(dict_T*),
 		    compare_readdirex_item);
 	else
-# endif
+	    qsort((void*)gap->ga_data, (size_t)gap->ga_len, sizeof(char_u *),
+		    compare_readdir_item);
+# else
 	    sort_strings((char_u **)gap->ga_data, gap->ga_len);
+# endif
     }
 
     return failed ? FAIL : OK;
@@ -4883,7 +4910,7 @@
 	exp = vim_strsave(name);
 	if (exp == NULL)
 	    return -1;
-	if (readdir_core(&ga, exp, FALSE, NULL, NULL) == OK)
+	if (readdir_core(&ga, exp, FALSE, NULL, NULL, READDIR_SORT_NONE) == OK)
 	{
 	    for (i = 0; i < ga.ga_len; ++i)
 	    {
diff --git a/src/filepath.c b/src/filepath.c
index 90d04cf..1fe757e 100644
--- a/src/filepath.c
+++ b/src/filepath.c
@@ -1405,6 +1405,36 @@
     return retval;
 }
 
+    static int
+readdirex_dict_arg(typval_T *tv, int *cmp)
+{
+    char_u     *compare;
+
+    if (tv->v_type != VAR_DICT)
+    {
+	emsg(_(e_dictreq));
+	return FAIL;
+    }
+
+    if (dict_find(tv->vval.v_dict, (char_u *)"sort", -1) != NULL)
+	compare = dict_get_string(tv->vval.v_dict, (char_u *)"sort", FALSE);
+    else
+    {
+	semsg(_(e_no_dict_key), "sort");
+	return FAIL;
+    }
+
+    if (STRCMP(compare, (char_u *) "none") == 0)
+	*cmp = READDIR_SORT_NONE;
+    else if (STRCMP(compare, (char_u *) "case") == 0)
+	*cmp = READDIR_SORT_BYTE;
+    else if (STRCMP(compare, (char_u *) "icase") == 0)
+	*cmp = READDIR_SORT_IC;
+    else if (STRCMP(compare, (char_u *) "collate") == 0)
+	*cmp = READDIR_SORT_COLLATE;
+    return OK;
+}
+
 /*
  * "readdir()" function
  */
@@ -1417,14 +1447,19 @@
     char_u	*p;
     garray_T	ga;
     int		i;
+    int         sort = READDIR_SORT_BYTE;
 
     if (rettv_list_alloc(rettv) == FAIL)
 	return;
     path = tv_get_string(&argvars[0]);
     expr = &argvars[1];
 
+    if (argvars[1].v_type != VAR_UNKNOWN && argvars[2].v_type != VAR_UNKNOWN &&
+	    readdirex_dict_arg(&argvars[2], &sort) == FAIL)
+	return;
+
     ret = readdir_core(&ga, path, FALSE, (void *)expr,
-	    (expr->v_type == VAR_UNKNOWN) ? NULL : readdir_checkitem);
+	    (expr->v_type == VAR_UNKNOWN) ? NULL : readdir_checkitem, sort);
     if (ret == OK)
     {
 	for (i = 0; i < ga.ga_len; i++)
@@ -1480,14 +1515,19 @@
     char_u	*path;
     garray_T	ga;
     int		i;
+    int         sort = READDIR_SORT_BYTE;
 
     if (rettv_list_alloc(rettv) == FAIL)
 	return;
     path = tv_get_string(&argvars[0]);
     expr = &argvars[1];
 
+    if (argvars[1].v_type != VAR_UNKNOWN && argvars[2].v_type != VAR_UNKNOWN &&
+	    readdirex_dict_arg(&argvars[2], &sort) == FAIL)
+	return;
+
     ret = readdir_core(&ga, path, TRUE, (void *)expr,
-	    (expr->v_type == VAR_UNKNOWN) ? NULL : readdirex_checkitem);
+	    (expr->v_type == VAR_UNKNOWN) ? NULL : readdirex_checkitem, sort);
     if (ret == OK)
     {
 	for (i = 0; i < ga.ga_len; i++)
diff --git a/src/globals.h b/src/globals.h
index cb85bcc..bbc12ce 100644
--- a/src/globals.h
+++ b/src/globals.h
@@ -1699,6 +1699,8 @@
 EXTERN char e_unknown_option[]	INIT(= N_("E113: Unknown option: %s"));
 EXTERN char e_letunexp[]	INIT(= N_("E18: Unexpected characters in :let"));
 EXTERN char e_reduceempty[]	INIT(= N_("E998: Reduce of an empty %s with no initial value"));
+// TODO: Change Error Number
+EXTERN char e_no_dict_key[]	INIT(= N_("E999: Dictionary with key \"%s\" required"));
 #endif
 #ifdef FEAT_QUICKFIX
 EXTERN char e_readerrf[]	INIT(= N_("E47: Error while reading errorfile"));
diff --git a/src/proto/fileio.pro b/src/proto/fileio.pro
index 2171e6b..cdf9274 100644
--- a/src/proto/fileio.pro
+++ b/src/proto/fileio.pro
@@ -31,7 +31,7 @@
 void buf_reload(buf_T *buf, int orig_mode);
 void buf_store_time(buf_T *buf, stat_T *st, char_u *fname);
 void write_lnum_adjust(linenr_T offset);
-int readdir_core(garray_T *gap, char_u *path, int withattr, void *context, int (*checkitem)(void *context, void *item));
+int readdir_core(garray_T *gap, char_u *path, int withattr, void *context, int (*checkitem)(void *context, void *item), int sort);
 int delete_recursive(char_u *name);
 void vim_deltempdir(void);
 char_u *vim_tempname(int extra_char, int keep);
diff --git a/src/testdir/test_cmdline.vim b/src/testdir/test_cmdline.vim
index 98af482..eeb9c2f 100644
--- a/src/testdir/test_cmdline.vim
+++ b/src/testdir/test_cmdline.vim
@@ -604,10 +604,20 @@
 endfunc
 
 func Test_cmdline_complete_languages()
+  let lang = substitute(execute('language time'), '.*"\(.*\)"$', '\1', '')
+  call assert_equal(lang, v:lc_time)
+
+  let lang = substitute(execute('language ctype'), '.*"\(.*\)"$', '\1', '')
+  call assert_equal(lang, v:ctype)
+
+  let lang = substitute(execute('language collate'), '.*"\(.*\)"$', '\1', '')
+  call assert_equal(lang, v:collate)
+
   let lang = substitute(execute('language messages'), '.*"\(.*\)"$', '\1', '')
+  call assert_equal(lang, v:lang)
 
   call feedkeys(":language \<c-a>\<c-b>\"\<cr>", 'tx')
-  call assert_match('^"language .*\<ctype\>.*\<messages\>.*\<time\>', @:)
+  call assert_match('^"language .*\<collate\>.*\<ctype\>.*\<messages\>.*\<time\>', @:)
 
   call assert_match('^"language .*\<' . lang . '\>', @:)
 
@@ -619,6 +629,9 @@
 
   call feedkeys(":language time \<c-a>\<c-b>\"\<cr>", 'tx')
   call assert_match('^"language .*\<' . lang . '\>', @:)
+
+  call feedkeys(":language collate \<c-a>\<c-b>\"\<cr>", 'tx')
+  call assert_match('^"language .*\<' . lang . '\>', @:)
 endfunc
 
 func Test_cmdline_complete_env_variable()
diff --git a/src/testdir/test_functions.vim b/src/testdir/test_functions.vim
index d9f8b9a..cefeaf7 100644
--- a/src/testdir/test_functions.vim
+++ b/src/testdir/test_functions.vim
@@ -1937,6 +1937,85 @@
   eval 'Xdir'->delete('rf')
 endfunc
 
+func Test_readdirex_sort()
+  CheckUnix
+  " Skip tests on Mac OS X and Cygwin (does not allow several files with different casing)
+  if has("osxdarwin") || has("osx") || has("macunix") || has("win32unix")
+    throw 'Skipped: Test_readdirex_sort on systems that do not allow this using the default filesystem'
+  endif
+  let _collate = v:collate
+  call mkdir('Xdir2')
+  call writefile(['1'], 'Xdir2/README.txt')
+  call writefile(['2'], 'Xdir2/Readme.txt')
+  call writefile(['3'], 'Xdir2/readme.txt')
+
+  " 1) default
+  let files = readdirex('Xdir2')->map({-> v:val.name})
+  let default = copy(files)
+  call assert_equal(['README.txt', 'Readme.txt', 'readme.txt'], files, 'sort using default')
+
+  " 2) no sorting
+  let files = readdirex('Xdir2', 1, #{sort: 'none'})->map({-> v:val.name})
+  let unsorted = copy(files)
+  call assert_equal(['README.txt', 'Readme.txt', 'readme.txt'], sort(files), 'unsorted')
+
+  " 3) sort by case (same as default)
+  let files = readdirex('Xdir2', 1, #{sort: 'case'})->map({-> v:val.name})
+  call assert_equal(default, files, 'sort by case')
+
+  " 4) sort by ignoring case
+  let files = readdirex('Xdir2', 1, #{sort: 'icase'})->map({-> v:val.name})
+  call assert_equal(unsorted->sort('i'), files, 'sort by icase')
+
+  " 5) Default Collation
+  let collate = v:collate
+  lang collate C
+  let files = readdirex('Xdir2', 1, #{sort: 'collate'})->map({-> v:val.name})
+  call assert_equal(['README.txt', 'Readme.txt', 'readme.txt'], files, 'sort by C collation')
+
+  " 6) Collation de_DE
+  " Switch locale, this may not work on the CI system, if the locale isn't
+  " available
+  try
+    lang collate de_DE
+    let files = readdirex('Xdir2', 1, #{sort: 'collate'})->map({-> v:val.name})
+    call assert_equal(['readme.txt', 'Readme.txt', 'README.txt'], files, 'sort by de_DE collation')
+  catch
+    throw 'Skipped: de_DE collation is not available'
+
+  finally
+    exe 'lang collate' collate
+    eval 'Xdir2'->delete('rf')
+  endtry
+endfunc
+
+func Test_readdir_sort()
+  " some more cases for testing sorting for readdirex
+  let dir = 'Xdir3'
+  call mkdir(dir)
+  call writefile(['1'], dir .. '/README.txt')
+  call writefile(['2'], dir .. '/Readm.txt')
+  call writefile(['3'], dir .. '/read.txt')
+  call writefile(['4'], dir .. '/Z.txt')
+  call writefile(['5'], dir .. '/a.txt')
+  call writefile(['6'], dir .. '/b.txt')
+
+  " 1) default
+  let files = readdir(dir)
+  let default = copy(files)
+  call assert_equal(default->sort(), files, 'sort using default')
+
+  " 2) sort by case (same as default)
+  let files = readdir(dir, '1', #{sort: 'case'})
+  call assert_equal(default, files, 'sort using default')
+
+  " 3) sort by ignoring case
+  let files = readdir(dir, '1', #{sort: 'icase'})
+  call assert_equal(default->sort('i'), files, 'sort by ignoring case')
+
+  eval dir->delete('rf')
+endfunc
+
 func Test_delete_rf()
   call mkdir('Xdir')
   call writefile([], 'Xdir/foo.txt')
diff --git a/src/version.c b/src/version.c
index 979ce70..e1a41fb 100644
--- a/src/version.c
+++ b/src/version.c
@@ -755,6 +755,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    988,
+/**/
     987,
 /**/
     986,
diff --git a/src/vim.h b/src/vim.h
index 0204aa3..2c2848c 100644
--- a/src/vim.h
+++ b/src/vim.h
@@ -1599,6 +1599,11 @@
 #  define STRICMP(d, s)	    vim_stricmp((char *)(d), (char *)(s))
 # endif
 #endif
+#ifdef HAVE_STRCOLL
+# define STRCOLL(d, s)     strcoll((char *)(d), (char *)(s))
+#else
+# define STRCOLL(d, s)     strcmp((char *)(d), (char *)(s))
+#endif
 
 // Like strcpy() but allows overlapped source and destination.
 #define STRMOVE(d, s)	    mch_memmove((d), (s), STRLEN(s) + 1)
@@ -1896,7 +1901,7 @@
 #define VALID_PATH		1
 #define VALID_HEAD		2
 
-// Defines for Vim variables.  These must match vimvars[] in eval.c!
+// Defines for Vim variables.  These must match vimvars[] in evalvars.c!
 #define VV_COUNT	0
 #define VV_COUNT1	1
 #define VV_PREVCOUNT	2
@@ -1992,7 +1997,8 @@
 #define VV_VERSIONLONG	92
 #define VV_ECHOSPACE	93
 #define VV_ARGV		94
-#define VV_LEN		95	// number of v: vars
+#define VV_COLLATE      95
+#define VV_LEN		96	// number of v: vars
 
 // used for v_number in VAR_BOOL and VAR_SPECIAL
 #define VVAL_FALSE	0L	// VAR_BOOL
@@ -2669,4 +2675,10 @@
 #define FSK_IN_STRING	0x04	// TRUE in string, double quote is escaped
 #define FSK_SIMPLIFY	0x08	// simplify <C-H> and <A-x>
 
+// Flags for the readdirex function, how to sort the result
+#define READDIR_SORT_NONE	0  // do not sort
+#define READDIR_SORT_BYTE	1  // sort by byte order (strcmp), default
+#define READDIR_SORT_IC		2  // sort ignoring case (strcasecmp)
+#define READDIR_SORT_COLLATE	3  // sort according to collation (strcoll)
+
 #endif // VIM__H