A♯ (A-sharp; also called la dièse) is the eleventh semitone of the solfège. In some countries (where B is known as H), it is also called B.

This note lies a chromatic semitone above A and a diatonic semitone below B, thus being enharmonic to si bémol or B♭ (B-flat).

When calculated in equal temperament with a reference of A above middle C as 440 Hz, the frequency of the A♯ above middle C is approximately 466.164Hz.^[1] See pitch (music) for a discussion of historical variations in frequency.

• B♭ (musical note), an enharmonic note
• Piano key frequencies
• A-sharp major
• A-sharp minor
• Root (chord)