| Honorific-Prefix: | Most Reverend |
| Alfonso de Fonseca | |
| Bishop of Osma | |
| Church: | Catholic Church |
| Diocese: | Diocese of Osma |
| Term: | 1493–1505 |
| Predecessor: | Raffaele Sansone Riario |
| Successor: | Alfonso Enríquez |
| Consecration: | 25 February 1470 |
| Consecrated By: | Giacopo Antonio Venier |
| Birth Date: | [1] |
| Birth Place: | Toro, Zamora[2] |
| Death Place: | Seville |
| Previous Post: | Bishop of Ávila (1469–1485) Bishop of Cuenca (1485–1493) |
| Nationality: | Spanish |
Alfonso de Fonseca (1422 - 1505) was a Roman Catholic prelate who served as Bishop of Osma (1493–1505), Bishop of Cuenca (1485–1493),[3] and Bishop of Ávila (1469–1485).[4]
Alfonso was the first son of Pedro de Ulloa y Fonesca and Isabel de Quijada.[2]
On 29 January 1469, in order to thank his services to the Spanish crown,[1] Alfonso was appointed by the King of Spain and confirmed by Pope Paul II as Bishop of Ávila. On 25 February 1470, he was ordained bishop by Giacopo Antonio Venier, Bishop of Cuenca; Giovanni Gianderoni, Bishop of Città di Castello; and Corrado Marcellini, Bishop of Montefeltro. On 26 August 1485, he was appointed by Pope Innocent VIII as Bishop of Cuenca. On 24 May 1493, he was appointed by Pope Alexander VI as Bishop of Osma, where he served until his death in 1505.