Alfonso Gesualdo di Conza (20 October 1540–14 February 1603) was an Italian Cardinal, from 1561. He was from Naples. His attendance at the papal conclave of 1565-6 at the age of only 25 makes him one of the youngest Cardinals ever to participate in a papal election.
He was archbishop of Conza in 1564, bishop of Albano in 1583, bishop of Frascati in 1587, bishop of Porto e Santa Rufina in 1589, bishop of Ostia in 1591, archbishop of Naples in 1596.
He was a patron of Sant'Andrea della Valle, in Rome, the mother church of the Theatine Order. The composer Carlo Gesualdo was his nephew.