diff --git a/mercurial/debugcommands.py b/mercurial/debugcommands.py
--- a/mercurial/debugcommands.py
+++ b/mercurial/debugcommands.py
@@ -3786,8 +3786,21 @@ def debugsub(ui, repo, rev=None):
         ui.writenoi18n(b' revision %s\n' % v[1])
 
 
-@command(b'debugshell', optionalrepo=True)
-def debugshell(ui, repo):
+@command(
+    b'debugshell',
+    [
+        (
+            b'c',
+            b'command',
+            b'',
+            _(b'program passed in as a string'),
+            _(b'COMMAND'),
+        )
+    ],
+    _(b'[-c COMMAND]'),
+    optionalrepo=True,
+)
+def debugshell(ui, repo, **opts):
     """run an interactive Python interpreter
 
     The local namespace is provided with a reference to the ui and
@@ -3815,6 +3828,12 @@ def debugshell(ui, repo):
         except ImportError:
             site = None  # Keep PyCharm happy
 
+    command = opts.get('command')
+    if command:
+        compiled = code.compile_command(encoding.strfromlocal(command))
+        code.InteractiveInterpreter(locals=imported_objects).runcode(compiled)
+        return
+
     code.interact(local=imported_objects)
 
 
diff --git a/tests/test-completion.t b/tests/test-completion.t
--- a/tests/test-completion.t
+++ b/tests/test-completion.t
@@ -328,7 +328,7 @@ Show all commands + options
   debugrevspec: optimize, show-revs, show-set, show-stage, no-optimized, verify-optimized
   debugserve: sshstdio, logiofd, logiofile
   debugsetparents: 
-  debugshell: 
+  debugshell: command
   debugsidedata: changelog, manifest, dir
   debugssl: 
   debugstrip: rev, force, no-backup, nobackup, , keep, bookmark, soft
diff --git a/tests/test-debugcommands.t b/tests/test-debugcommands.t
--- a/tests/test-debugcommands.t
+++ b/tests/test-debugcommands.t
@@ -724,3 +724,8 @@ Test debugpeer
   pushable: yes
 
 #endif
+
+Test debugshell
+
+  $ hg debugshell -c 'ui.write(b"%s\n" % ui.username())'
+  test