The Blackmar Gambit arises after 1.d4 d5 2.e4. ECO code: D00.

Named after Armand Blackmar (1826–1888). White immediately challenges the centre with e4. After 2...dxe4, the Blackmar-Diemer Gambit arises with 3.Nc3 (or 3.f3). White sacrifices a pawn for rapid piece development and attacking chances. The gambit is playable at club level but not considered fully sound.