- Source: W21 (disambiguation)
The W21 was an hydrogen bomb design for the US military.
W21 may also refer to:
British NVC community W21, a scrub community in the British National Vegetation Classification system
Mercedes-Benz W21, a German sedan
Samsung W21 5G, a smartphone
Wanderer W21, a German sedan
Wilderness 21, an American sailboat
The AIATSIS designation for the Tharrkari language
The Wenninger index number for a Great dodecahedron