| Type: | Bishop |
| Honorific-Prefix: | Most Reverend |
| Tomás Casillas | |
| Bishop of Chiapas | |
| Church: | Catholic Church |
| Term: | 1552–1567 |
| Predecessor: | Bartolomé de las Casas |
| Successor: | Pedro Martín Fernández |
| Consecration: | 1552 |
| Consecrated By: | Francisco Marroquín Hurtado |
| Birth Place: | León, Spain |
| Death Date: | 29 Oct 1567 |
Tomás Casillas, O.P. (died 1567) was a Roman Catholic prelate who served as Bishop of Chiapas (1552–1567).
Tomás Casillas was born in León, Spain and ordained a priest in the Order of Friars Preachers.On 19 Jan 1551, he was appointed during the papacy of Pope Julius III as Bishop of Chiapas.In 1552, he was consecrated bishop by Francisco Marroquín Hurtado, Bishop of Santiago de Guatemala In 1555, he attended the First Mexican Provincial Council.[1]
Casillas died on 29 Oct 1567.