B大调是一个基于B音的大调，由B、C♯、D♯、E、F♯、G♯、A♯和B组成，调号有五个升号。相对小调是升G小调，并行小调是B小调，与降C大调异名同音。

In music theory, B major is a major scale based on B. The pitches B, C♯, D♯, E, F♯, G♯, and A♯ are all part of the B major scale. Its key signature has five sharps.

B major's relative minor is G-sharp minor, its parallel minor is B minor, and its enharmonic equivalent is C-flat major.