diff --git a/src/CSET/operators/constraints.py b/src/CSET/operators/constraints.py
index 8935cbf6d..28c584fd7 100644
--- a/src/CSET/operators/constraints.py
+++ b/src/CSET/operators/constraints.py
@@ -14,6 +14,7 @@
 
 """Operators to generate constraints to filter with."""
 
+import re
 from collections.abc import Iterable
 from datetime import datetime
 
@@ -45,22 +46,25 @@ def generate_stash_constraint(stash: str, **kwargs) -> iris.AttributeConstraint:
 
 
 def generate_var_constraint(varname: str, **kwargs) -> iris.Constraint:
-    """Generate constraint from variable name.
+    """Generate constraint from variable name or STASH code.
 
-    Operator that takes a CF compliant variable name string, and uses iris to
-    generate a constraint to be passed into the read operator to minimize the
-    CubeList the read operator loads and speed up loading.
+    Operator that takes a CF compliant variable name string, and generates an
+    iris constraint to be passed into the read or filter operator. Can also be
+    passed a STASH code to generate a STASH constraint.
 
     Arguments
     ---------
     varname: str
-        CF compliant name of variable. Needed later for LFRic.
+        CF compliant name of variable, or a UM STASH code such as "m01s03i236".
 
     Returns
     -------
     varname_constraint: iris.Constraint
     """
-    varname_constraint = iris.Constraint(name=varname)
+    if re.match(r"m[0-9]{2}s[0-9]{2}i[0-9]{3}$", varname):
+        varname_constraint = iris.AttributeConstraint(STASH=varname)
+    else:
+        varname_constraint = iris.Constraint(name=varname)
     return varname_constraint
 
 
diff --git a/tests/operators/test_constraints.py b/tests/operators/test_constraints.py
index 74bb88026..b372f9d4a 100644
--- a/tests/operators/test_constraints.py
+++ b/tests/operators/test_constraints.py
@@ -33,6 +33,13 @@ def test_generate_var_constraint():
     assert repr(var_constraint) == expected_var_constraint
 
 
+def test_generate_var_constraint_stash():
+    """Generate iris cube constraint for UM STASH code with var constraint."""
+    var_constraint = constraints.generate_var_constraint("m01s03i236")
+    expected_stash_constraint = "AttributeConstraint({'STASH': 'm01s03i236'})"
+    assert repr(var_constraint) == expected_stash_constraint
+
+
 def test_generate_cell_methods_constraint():
     """Generate iris cube constraint for cell methods."""
     cell_methods_constraint = constraints.generate_cell_methods_constraint([])