| Type: | Bishop |
| Honorific-Prefix: | Most Reverend |
| Agostino da Siena | |
| Bishop of Montemarano | |
| Church: | Catholic Church |
| Diocese: | Diocese of Montemarano |
| Term: | 1477–1484 |
| Predecessor: | Ladislao Dentice |
| Successor: | Simeone Dantici |
| Death Date: | 1484 |
Agostino da Siena, O.F.M. (died 1484) was a Roman Catholic prelate who served as Bishop of Montemarano (1477–1484).
Agostino da Siena was ordained a priest in the Order of Friars Minor.On 24 Jan 1477, he was appointed during the papacy of Pope Sixtus IV as Bishop of Montemarano.He served as Bishop of Montemarano until his death in 1484.