diff --git a/dvc/command/machine.py b/dvc/command/machine.py
--- a/dvc/command/machine.py
+++ b/dvc/command/machine.py
@@ -202,16 +202,32 @@ class CmdMachineStatus(CmdBase):
         "instance_gpu",
     ]
 
+    def _show_machine_status(self, name: str):
+        ui.write(f"machine '{name}':")
+        all_status = list(self.repo.machine.status(name))
+        if not all_status:
+            ui.write("\toffline")
+        for i, status in enumerate(all_status, start=1):
+            ui.write(f"\tinstance_num_{i}:")
+            for field in self.SHOWN_FIELD:
+                value = status.get(field, None)
+                ui.write(f"\t\t{field:20}: {value}")
+
     def run(self):
         if self.repo.machine is None:
             raise MachineDisabledError
 
-        all_status = self.repo.machine.status(self.args.name)
-        for i, status in enumerate(all_status, start=1):
-            ui.write(f"instance_num_{i}:")
-            for field in self.SHOWN_FIELD:
-                value = status.get(field, None)
-                ui.write(f"\t{field:20}: {value}")
+        if self.args.name:
+            self._show_machine_status(self.args.name)
+        else:
+            name_set = set()
+            for level in self.repo.config.LEVELS:
+                conf = self.repo.config.read(level)["machine"]
+                name_set.update(conf.keys())
+            name_list = list(name_set)
+            for name in sorted(name_list):
+                self._show_machine_status(name)
+
         return 0
 
 
@@ -390,7 +406,9 @@ def add_parser(subparsers, parent_parser):
     )
     machine_create_parser.set_defaults(func=CmdMachineCreate)
 
-    machine_STATUS_HELP = "List the status of a running machine."
+    machine_STATUS_HELP = (
+        "List the status of running instances for one/all machines."
+    )
     machine_status_parser = machine_subparsers.add_parser(
         "status",
         parents=[parent_config_parser, parent_parser],
@@ -399,7 +417,7 @@ def add_parser(subparsers, parent_parser):
         formatter_class=argparse.RawDescriptionHelpFormatter,
     )
     machine_status_parser.add_argument(
-        "name", help="Name of the running machine."
+        "name", nargs="?", help="(optional) Name of the machine."
     )
     machine_status_parser.set_defaults(func=CmdMachineStatus)
 

diff --git a/tests/func/machine/test_machine_status.py b/tests/func/machine/test_machine_status.py
--- a/tests/func/machine/test_machine_status.py
+++ b/tests/func/machine/test_machine_status.py
@@ -8,6 +8,7 @@ def test_status(
     status = machine_instance
     assert main(["machine", "status", "foo"]) == 0
     cap = capsys.readouterr()
-    assert "instance_num_1:" in cap.out
+    assert "machine 'foo':\n" in cap.out
+    assert "\tinstance_num_1:\n" in cap.out
     for key in CmdMachineStatus.SHOWN_FIELD:
-        assert f"\t{key:20}: {status[key]}" in cap.out
+        assert f"\t\t{key:20}: {status[key]}\n" in cap.out
diff --git a/tests/unit/command/test_machine.py b/tests/unit/command/test_machine.py
--- a/tests/unit/command/test_machine.py
+++ b/tests/unit/command/test_machine.py
@@ -1,4 +1,5 @@
 import configobj
+from mock import call
 
 from dvc.cli import parse_args
 from dvc.command.machine import (
@@ -19,6 +20,8 @@
             "[feature]\n"
             "  machine = true\n"
             "['machine \"foo\"']\n"
+            "  cloud = aws\n"
+            "['machine \"myaws\"']\n"
             "  cloud = aws"
         )
     }
@@ -42,7 +45,7 @@ def test_remove(tmp_dir):
     cmd = cli_args.func(cli_args)
     assert cmd.run() == 0
     config = configobj.ConfigObj(str(tmp_dir / ".dvc" / "config"))
-    assert list(config.keys()) == ["feature"]
+    assert list(config.keys()) == ["feature", 'machine "myaws"']
 
 
 def test_create(tmp_dir, dvc, mocker):
@@ -58,7 +61,8 @@ def test_create(tmp_dir, dvc, mocker):
     m.assert_called_once_with("foo")
 
 
-def test_status(tmp_dir, dvc, mocker):
+def test_status(tmp_dir, scm, dvc, mocker):
+    tmp_dir.gen(DATA)
     cli_args = parse_args(["machine", "status", "foo"])
     assert cli_args.func == CmdMachineStatus
 
@@ -66,10 +70,18 @@ def test_status(tmp_dir, dvc, mocker):
     m = mocker.patch.object(
         cmd.repo.machine, "status", autospec=True, return_value=[]
     )
-
     assert cmd.run() == 0
     m.assert_called_once_with("foo")
 
+    cli_args = parse_args(["machine", "status"])
+    cmd = cli_args.func(cli_args)
+    m = mocker.patch.object(
+        cmd.repo.machine, "status", autospec=True, return_value=[]
+    )
+    assert cmd.run() == 0
+    assert m.call_count == 2
+    m.assert_has_calls([call("foo"), call("myaws")])
+
 
 def test_destroy(tmp_dir, dvc, mocker):
     cli_args = parse_args(["machine", "destroy", "foo"])

machine: show all machines in `status`
Make the `name` argument optional in `dvc machines status` so that all machines may be shown at once. Extracted from https://github.com/iterative/dvc/pull/6649#issuecomment-946940057.

tests/func/machine/test_machine_status.py::test_status tests/unit/command/test_machine.py::test_status
tests/unit/command/test_machine.py::test_create tests/unit/command/test_machine.py::test_ssh tests/unit/command/test_machine.py::test_rename tests/unit/command/test_machine.py::test_destroy tests/unit/command/test_machine.py::test_add tests/unit/command/test_machine.py::test_list tests/unit/command/test_machine.py::test_modified tests/unit/command/test_machine.py::test_remove