F♯ (F-sharp; also known as fa dièse or fi) is the seventh semitone of the solfège.

It lies a chromatic semitone above F and a diatonic semitone below G, thus being enharmonic to sol bémol or G♭ (G-flat) in 12 equal temperament. However, in other temperaments, such as quarter-comma meantone, it is not the same as G♭. G♭ is a major third below B♭, whereas F♯ is a major third above D (a minor third below A). Another enharmonic note is E (E-double sharp).

When calculated in equal temperament with a reference of A above middle C as 440 Hz, the frequency of the F♯ above middle C (or F♯₄) is approximately 369.994Hz.^[1] See pitch (music) for a discussion of historical variations in frequency.