C-sharp major is a major scale based on C sharp, consisting of the pitches C-sharp, D-sharp, E-sharp (enharmonic to F natural), F-sharp, G sharp, A sharp, B sharp (enharmonic to C natural) and C sharp. Its key signature consists of seven sharps.
 | |
| Relative key | A# minor |
|---|---|
| Parallel key | Db major |
| Component pitches | |
| C#, D#, E#, F#, G#, A#, B# | |
- Also see: C-sharp minor, or C major.
Its relative minor is A sharp minor, and its parallel minor is C sharp minor. Its enharmonic equivalent is D flat major.
A harp tuned to C-sharp major has all its pedals in the bottom position. Because all the strings are then pinched and shortened, this is the least resonant key for the instrument.
Although most composers prefer to use the enharmonic equivalent D-flat major because it has just five flats as opposed to the seven sharps of C-sharp major, Johann Sebastian Bach actually chose C sharp major for Prelude and Fugue No. 3 in both books of the Well-Tempered Clavier. Béla Bartók's String Quartet No. 3 is one of the few in C sharp major. In Hungarian Rhapsody No. 6, Franz Liszt actually changes key from D flat major to C sharp major near the beginning of the piece. Maurice Ravel selected C sharp major as the tonic key of Ondine from his piano suite Gaspard de la nuit.