English conspirator during the reign of Elizabeth I, seeking the release of Mary, Queen of Scots, and the free exercise of the Roman Catholic religion.

His father, Sir Thomas Percy (son of the 5th earl), was attainted and executed at Tyburn for his part in the Yorkshire rebellion of 1536 called the Pilgrimage of Grace (q.v.). His brother, the 6th earl, fearing the consequences, surrendered his estates, and the title fell into abeyance on his death the following year. In 1557, after faithful military service, Thomas Percy was made 7th earl of Northumberland.

Other honours and services followed, but his Catholicism made him an object of suspicion at the Elizabethan court, and he was passed over in various preferments that he thought due him. After Mary, Queen of Scots, crossed into England and was imprisoned, Northumberland sympathized with her misfortune, as the victim of his faith. By 1569 he was in communication with Spanish envoys and, late that year, joined like-minded nobles in issuing proclamations promising the release of Mary and the restoration of the Catholic religion. Within a month (December 1569) the northern rebels were scattered or killed by government forces, and Northumberland escaped to Scotland. At long last, in August 1572, the Scots handed him over to Elizabeth's officers on payment of £2,000. He was beheaded in the marketplace at York.