Dom Thomas de Castro (c.1621-1684) was a native of Divar in Goa, Portuguese India.
It is recorded that in Rome he was appointed professor of Philosophy and Theology and Prefect of the aspirants for various sacerdotal degrees.
On 30 August 1675, the Holy See appointed him the Vicar Apostolic for the kingdoms of Cochin, Tamor, Madurai, Mysore, Cranganore, Cannanore and the Coast of Canara.
He also remained the Vicar Apostolic of the Latin Catholic Archdiocese of Verapoly (1675–1689), in present-day Varappuzha in Kerala.
Bishop de Castro died in Mangalore on 16 July 1684 at the age of 68 years, his grave in the Milagres Church cemetery can be identified by a bronze slab next to the St. Monica Chapel.