diff --git a/nox/_options.py b/nox/_options.py
index 6b6bfef0..9481ed37 100644
--- a/nox/_options.py
+++ b/nox/_options.py
@@ -316,8 +316,8 @@ def _session_completer(
         noxfile=True,
         merge_func=_default_venv_backend_merge_func,
         help="Virtual environment backend to use by default for nox sessions, this is ``'virtualenv'`` by default but "
-        "any of ``('virtualenv', 'conda', 'venv')`` are accepted.",
-        choices=["none", "virtualenv", "conda", "venv"],
+        "any of ``('virtualenv', 'conda', 'mamba', 'venv')`` are accepted.",
+        choices=["none", "virtualenv", "conda", "mamba", "venv"],
     ),
     _option_set.Option(
         "force_venv_backend",
@@ -327,9 +327,9 @@ def _session_completer(
         noxfile=True,
         merge_func=_force_venv_backend_merge_func,
         help="Virtual environment backend to force-use for all nox sessions in this run, overriding any other venv "
-        "backend declared in the nox file and ignoring the default backend. Any of ``('virtualenv', 'conda', 'venv')`` "
+        "backend declared in the nox file and ignoring the default backend. Any of ``('virtualenv', 'conda', 'mamba', 'venv')`` "
         "are accepted.",
-        choices=["none", "virtualenv", "conda", "venv"],
+        choices=["none", "virtualenv", "conda", "mamba", "venv"],
     ),
     _option_set.Option(
         "no_venv",
diff --git a/nox/sessions.py b/nox/sessions.py
index ff4b30a4..a71b6789 100644
--- a/nox/sessions.py
+++ b/nox/sessions.py
@@ -674,7 +674,7 @@ def _create_venv(self) -> None:
             )
         else:
             raise ValueError(
-                f"Expected venv_backend one of ('virtualenv', 'conda', 'venv'), but got '{backend}'."
+                f"Expected venv_backend one of ('virtualenv', 'conda', 'mamba', 'venv'), but got '{backend}'."
             )
 
         self.venv.create()