Saint Thomas Garnet (c.1575 – 23 June 1608) was a Jesuit priest who was executed in London. He is the protomartyr (i.e., the first martyr associated with a place) of Saint Omer and therefore of Stonyhurst College. He was executed at Tyburn and is one of the Forty Martyrs of England and Wales.
Thomas Garnet was born into a prominent family in Southwark. His uncle, Henry Garnet, was the superior of the Jesuits in England. Richard Garnet, Thomas's father, was at Balliol College, Oxford, at the time when great severity began to be used against Catholics. His example provided leadership to a generation of Oxford men which was to produce Edmund Campion, Robert Persons and other English Catholics.
Thomas attended Collyer's School in Horsham, Sussex, and was afterwards a page to one of the half-brothers of Philip Howard, Earl of Arundel, who were, however, conformists (i.e. conformed to the Anglican faith).
Because English colleges had been turned over to Protestants, English Catholics had to go to the continent for their education. Thomas, at age 17, was amongst the first students of Saint Omer's Jesuit College (at Stonyhurst since 1794) in 1593. By 1595 he was considered fit for Saint Albans, the new English seminary at Valladolid. In January he set out from Calais with five others from Calais, John Copley, William Worthington, John Ivreson, James Thomson, and Henry Mompesson.