Sixtus refers to a name used by several popes in the history of the Roman Catholic Church. The most notable among them is Pope Sixtus V, who reigned from 1585 to 1590. He is known for his significant reforms in the church and the administration of Rome, as well as for commissioning the construction of the Papal Basilica of St. Peter. Another important figure is Pope Sixtus IV, who served from 1471 to 1484. He is recognized for establishing the Sistine Chapel, which is famous for its stunning frescoes painted by Michelangelo. Both popes played crucial roles in shaping the church and its influence during the Renaissance period.