Ippolito (I) d'Este (Hungarian: Estei Hippolit; March 20, 1479 – September 3, 1520) was an Italian Roman Catholic cardinal, and Archbishop of Esztergom. He was a member of the House of Este.
Born in Ferrara, he was the son of Duke Ercole I d'Este and Eleanor of Naples and was immediately educated for a career in the Church. In 1485, at the age of six, he was already at the head of an abbacy, and two years later, thanks to his aunt Beatrix of Aragon, who had married King Matthias Corvinus of Hungary, he was named archbishop of Esztergom in Hungary. The latter election was not confirmed by Pope Innocent VIII until he was eighteen; in the meantime Ippolito studied for seven years at the Hungarian court.
After Matthias' death, he travelled frequently to Italy. During one of these trips, he was created cardinal by Alexander VI, on September 20, 1493. Three years later he returned to Italy to escape the plague that was striking Hungary and arrived in Rome with a following of 250 people. He was appointed archbishop of Milan in 1497 and named cardinal in 1509, after which he resided in Rome and governed the archdiocese of Milan through a vicar. According to the tax reports of the Curia for the year 1500, he was the fifth richest member. His influence grew further when his brother Alfonso married Lucrezia Borgia, daughter of Alexander VI, who granted him the title of archipresbyter of St. Peter's. He remained in Rome until February 15, 1503, although his relationship with the pope later deteriorated due to Ercole's philo-French maneuvers.