Alexandrine-Caroline Branchu (November 2, 1780 – October 14, 1850) was a French opera soprano. She was born in Cap-Haïtien, Haïti at a time when Haiti was a French colony. A gifted vocalist, for the better part of the first quarter of the 19th century, she was the leading soprano at the Paris Opéra.
Branchu was one of the first students at the Paris Conservatoire after it opened in 1795, and studied singing under Pierre Garat.
Although Branchu frequently performed works by Christoph Willibald Gluck and was notable for the Anacreon overture and Les Abencérages by Luigi Cherubini, she is best remembered for her performances in the title role of Gaspare Spontini's most important opera, La vestale (1807). She also performed in Spontini's Fernand Cortez (1809) and Olympie (1819). She was briefly a mistress of Napoleon.
Branchu died in the Parisian suburb of Passy and was buried in the Père Lachaise Cemetery.