Giles Antonini, O.E.S.A., commonly referred to as Giles of Viterbo, was a 16th-century Italian Augustinian friar, bishop of Viterbo and cardinal, a reforming theologian, orator, humanist and poet. He was born in Viterbo and died in Rome.

Viterbo is a city and comune (municipality) in the Lazio region of Italy, the capital of the province of Viterbo.