B40

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