B51 or B-51 may be:
- HLA-B51, an HLA-B serotype
- Bundesstraße 51, a road in western Germany
- Martin XB-51, an American airplane
- Sicilian Defence in the Encyclopaedia of Chess Openings
- B51 (New York City bus)
disambiguation page lists articles associated with the same title formed as a letter-number combination.
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