| Martim Afonso de Castro | |
| Office: | Viceroy of Portuguese India |
| Term Start: | 1605 |
| Term End: | 1607 |
| Predecessor: | Aires de Saldanha |
| Successor: | Aleixo de Meneses |
| Birth Date: | c. 1560 |
| Birth Place: | Kingdom of Portugal |
| Death Place: | Portuguese Malacca |
| Nationality: | Portuguese |
| Allegiance: | Portuguese Empire |
| Battles: | Aceh expedition (1606) Dutch-Portuguese War |
Martim Afonso de Castro (died 3 June 1607 in Malacca) was a Portuguese Viceroy of India. He commanded the Portuguese Navy in the Battle of Cape Rachado and fought over the present day Malaccan exclave of Tanjung Tuan in 1606.[1] [2]