English conspirator, the central figure in the unsuccessful Throckmorton Plot to overthrow Queen Elizabeth I.

Throckmorton came from a staunch Roman Catholic family and was the nephew of Sir Nicholas Throckmorton, a diplomat for Elizabeth. After receiving his education at the University of Oxford, he traveled to the Continent in 1580, where he met Catholic exiles from England who were plotting against Elizabeth's Protestant regime. He returned in 1583 as an agent for a conspiracy involving France and Spain. Under the plan England was to be invaded by a French force under Henri, duc de Guise, who would free Elizabeth's prisoner Mary, Queen of Scots, and restore papal authority.

In London, Throckmorton occupied a house that served as a centre of communication between Mary and foreign agents. But Francis Walsingham (Walsingham, Sir Francis), Elizabeth's principal secretary, uncovered the conspiracy and Throckmorton was arrested in November 1583. Tortured on the rack, he made a full confession. Throckmorton was tried in May 1584 and executed several months later. One of his chief contacts, the Spanish ambassador to England, Bernardino de Mendoza, was expelled from the country.