diff --git a/runtime/ftplugin/groff.vim b/runtime/ftplugin/groff.vim
index 3ebfa03c6e..f628525411 100644
--- a/runtime/ftplugin/groff.vim
+++ b/runtime/ftplugin/groff.vim
@@ -2,6 +2,7 @@
 " Language:  groff(7)
 " Maintainer: Eisuke Kawashima ( e.kawaschima+vim AT gmail.com )
 " Last Change: 2025 Apr 24
+" 2025 Jun 18 by Vim Project: update commentstring option (#17516)
 
 if exists('b:did_ftplugin')
   finish
@@ -11,5 +12,8 @@ let b:nroff_is_groff = 1
 
 runtime! ftplugin/nroff.vim
 
+setlocal commentstring=\\#\ %s
+setlocal comments=:\\#,:.\\\",:\\\",:'\\\",:'''
+
 let b:undo_ftplugin .= '| unlet! b:nroff_is_groff'
 let b:did_ftplugin = 1
diff --git a/runtime/ftplugin/nroff.vim b/runtime/ftplugin/nroff.vim
index cd2680ef58..24fcc9472a 100644
--- a/runtime/ftplugin/nroff.vim
+++ b/runtime/ftplugin/nroff.vim
@@ -9,6 +9,7 @@
 "	2025 Feb 12 by Wu, Zhenyu <wuzhenyu@ustc.edu> (matchit configuration #16619)
 "	2025 Apr 16 by Eisuke Kawashima (cpoptions #17121)
 "	2025 Apr 24 by Eisuke Kawashima (move options from syntax to ftplugin #17174)
+"	2025 Jun 18 by Vim Project: update commentstring option (#17516)
 
 if exists("b:did_ftplugin")
   finish
@@ -19,7 +20,7 @@ let s:cpo_save = &cpo
 set cpo&vim
 
 setlocal commentstring=.\\\"\ %s
-setlocal comments=:.\\\"
+setlocal comments=:.\\\",:\\\",:'\\\",:'''
 setlocal sections+=Sh
 setlocal define=.\s*de