B40, B-40, or B.40 may refer to:
Roads Autovia B-40, a Spanish motorway in Catalonia Bundesstraße 40, a German road
In Science Borospherene, B40, an allotropic cage-like molecule of pure boron HLA-B40, an HLA-B serotype
Military Vietnamese designation of the RPG-2, the first rocket-propelled grenade launcher designed in the Soviet Union BSA B40, a 350cc British motorcycle Blackburn B.40, an experimental Blackburn flying boat Rolls-Royce B40 Engine, an inline-four petrol engine primarily used in the Austin Champ Unterseeboot B-40, World War I Imperial Germany Navy submarine U-boat YB-40 Flying Fortress, an aircraft
Other 40 amp, type B – a standard circuit breaker current rating B40 Balkan Cities Network, an intercity organization between Balkans cities Sicilian Defence, Encyclopaedia of Chess Openings code