diff --git a/changelogs/fragments/solaris-setfacl-chmod-fallback.yml b/changelogs/fragments/solaris-setfacl-chmod-fallback.yml
new file mode 100644
index 00000000000..3a2d8082d5a
--- /dev/null
+++ b/changelogs/fragments/solaris-setfacl-chmod-fallback.yml
@@ -0,0 +1,2 @@
+bugfixes:
+  - become - work around setfacl not existing on modern Solaris (and possibly failing on some filesystems even when it does exist)
diff --git a/lib/ansible/plugins/action/__init__.py b/lib/ansible/plugins/action/__init__.py
index ccb9002fd0e..50114bdccad 100644
--- a/lib/ansible/plugins/action/__init__.py
+++ b/lib/ansible/plugins/action/__init__.py
@@ -576,6 +576,9 @@ class ActionBase(with_metaclass(ABCMeta, object)):
             setfacl_mode = 'r-x'
             # Apple patches their "file_cmds" chmod with ACL support
             chmod_acl_mode = '{0} allow read,execute'.format(become_user)
+            # POSIX-draft ACL specification. Solaris, maybe others.
+            # See chmod(1) on something Solaris-based for syntax details.
+            posix_acl_mode = 'A+user:{0}:rx:allow'.format(become_user)
         else:
             chmod_mode = 'rX'
             # TODO: this form fails silently on freebsd.  We currently
@@ -584,6 +587,8 @@ class ActionBase(with_metaclass(ABCMeta, object)):
             setfacl_mode = 'r-X'
             # Apple
             chmod_acl_mode = '{0} allow read'.format(become_user)
+            # POSIX-draft
+            posix_acl_mode = 'A+user:{0}:r:allow'.format(become_user)
 
         # Step 3a: Are we able to use setfacl to add user ACLs to the file?
         res = self._remote_set_user_facl(
@@ -639,7 +644,17 @@ class ActionBase(with_metaclass(ABCMeta, object)):
             if res['rc'] == 0:
                 return remote_paths
 
-        # Step 3e: Common group
+        # Step 3e: Try Solaris/OpenSolaris/OpenIndiana-sans-setfacl chmod
+        # Similar to macOS above, Solaris 11.4 drops setfacl and takes file ACLs
+        # via chmod instead. OpenSolaris and illumos-based distros allow for
+        # using either setfacl or chmod, and compatibility depends on filesystem.
+        # It should be possible to debug this branch by installing OpenIndiana
+        # (use ZFS) and going unpriv -> unpriv.
+        res = self._remote_chmod(remote_paths, posix_acl_mode)
+        if res['rc'] == 0:
+            return remote_paths
+
+        # Step 3f: Common group
         # Otherwise, we're a normal user. We failed to chown the paths to the
         # unprivileged user, but if we have a common group with them, we should
         # be able to chown it to that.
diff --git a/test/units/plugins/action/test_action.py b/test/units/plugins/action/test_action.py
index b31048c1dc2..f5af0ce7851 100644
--- a/test/units/plugins/action/test_action.py
+++ b/test/units/plugins/action/test_action.py
@@ -470,7 +470,15 @@ class TestActionBase(unittest.TestCase):
         action_base._remote_chmod.side_effect = raise_if_plus_a
         assertSuccess()
 
-        # Step 3e: Common group
+        # Step 3e: chmod A+ on Solaris
+        # We threw AnsibleAuthenticationFailure above, try Solaris fallback.
+        # Based on our lambda above, it should be successful.
+        action_base._remote_chmod.assert_called_with(
+            remote_paths,
+            'A+user:remoteuser2:r:allow')
+        assertSuccess()
+
+        # Step 3f: Common group
         def rc_1_if_chmod_acl(definitely_not_underscore, mode):
             rc = 0
             if mode in CHMOD_ACL_FLAGS: