Apollo et Hyacinthus is an opera, K. 38, written in 1767 by Wolfgang Amadeus Mozart, who was 11 years old at the time. It is Mozart's first true opera (when one considers that Die Schuldigkeit des ersten Gebotes is simply a sacred drama). It is in three acts. As is suggested by the name, the opera is based upon Greek mythology as told by Roman poet Ovid in his masterwork Metamorphoses. Interpreting this work, Rufinus Widl wrote the libretto in Latin.

The opera was first performed on 13 May 1767 at the Great Hall, Salzburg University. The myth follows that Hyacinth died accidentally from being struck on the head by a discus thrown by Apollo. However, another myth tells that it was the wind god Zephyrus who was actually responsible for the Hyacinth's death because Zephyrus, out of jealousy, blew the discus off course in order to injure and kill Hyacinth. When he died, Apollo made the hyacinth flower spring out from his spilled blood.

The librettist and priest, Rufinus Widl, modified Ovid's story (in which Apollo, Zephyrus, and Hyacinth clearly constituted a homosexual love triangle) to make it conform to the ethic, by changing the sexually desired character from Ovid's Hyacinth to Melia, his sister.