Alonso de Fonseca y Ulloa (also Alonso I de Fonseca) (died 1473) was a Roman Catholic prelate who served as Bishop of Ávila (1445–1454), Archbishop of Seville (1454–1465 and 1469–1473), and Archbishop of Santiago de Compostela (1465–1469).

In 1445, Alonso de Fonseca y Ulloa was appointed by the King of Spain and confirmed by Pope Eugene IV as Bishop of Ávila.

[1][2] On 4 February 1454, he was appointed by Pope Nicholas V as Archbishop of Seville.

[1] In 1465, he was appointed by Pope Paul II as Archbishop of Santiago de Compostela.

[1] In 1469, he was appointed by Pope Paul II to his prior position as Archbishop of Seville where he served until his death in 1473.