B51 or B-51 may refer to:
*
HLA-B51, an HLA-B serotype
*
Bundesstraße 51
The Bundesstraße 51 (translates from German ''Federal road'', abbreviated as B 51) runs from Bremen in south-west direction though Lower Saxony, North Rhine-Westphalia, Rhineland-Palatinate and Saarland, and ends at the French border in the tow ...
, a road in western Germany
*
Martin XB-51, an American airplane
*
Sicilian Defence
The Sicilian Defence is a chess opening that begins with the following moves:
:1. b:Chess Opening Theory/1. e4, e4 b:Chess Opening Theory/1. e4/1...c5, c5
The Sicilian is the most popular and best-scoring response to White's first move 1.e4. Ope ...
, in the Encyclopaedia of Chess Openings
*
B51 (New York City bus)
The Metropolitan Transportation Authority (MTA) operates a number of bus routes in Brooklyn, New York, United States; one minor route is privately operated under a city franchise. Many of them are the direct descendants of streetcar lines (see li ...
{{Letter-NumberCombDisambig