diff --git a/nn/loss.py b/nn/loss.py
index fef1d576..80d4a3a7 100644
--- a/nn/loss.py
+++ b/nn/loss.py
@@ -190,6 +190,18 @@ def kl_div(*, target: nn.Tensor, target_type: str,
   return kl
 
 
+@nn.scoped
+def mean_absolute_difference(a: nn.Tensor, b: nn.Tensor, *, axis: Optional[nn.Dim] = None) -> nn.Tensor:
+  """
+  Mean absolute difference, mean absolute error (MAE), or L1 loss between two tensors,
+  i.e. mean_{axis}( abs(a - b) ), where axis is the feature dim by default.
+  """
+  if not axis:
+    assert a.feature_dim
+    axis = a.feature_dim
+  return nn.reduce(nn.abs(a - b), mode="mean", axis=axis)
+
+
 @nn.scoped
 def mean_squared_difference(a: nn.Tensor, b: nn.Tensor, *, axis: Optional[nn.Dim] = None) -> nn.Tensor:
   """