Thomas Brett (1667–1743) was an English nonjuring clergyman known as an author.
He was the son of Thomas Brett of Spring Grove, Wye, Kent. His father descended from a family settled at Wye; his mother was Letitia, daughter of John Boys of Betshanger, Sandwich, where Brett was born. He was educated at Wye grammar school, under John Paris and Samuel Pratt (later dean of Rochester). On 20 March 1684 he was admitted pensioner of Queens' College, Cambridge. He was removed by his father for extravagance, but permitted to return. He then moved to Corpus Christi College on 17 January 1689. He took the LL.B. degree in 1690.
He was ordained deacon on 21 December 1690. After holding a curacy at Folkestone for a year he was ordained priest, and chosen lecturer at Islington. The vicar, Mr. Gery, encouraged him to exchange his early Whiggism for Tory and High Church principles. On the death of his father, his mother persuaded him to return (May 1696) to Spring Grove, where he undertook the cure of Great Chart. Here he married Bridget, daughter of Sir Nicholas Toke. In 1697 he became LL.D., and soon afterwards exchanged Great Chart for Wye. He became rector of Betshanger on the death of his uncle, Thomas Boys; and on 12 April 1705 Archbishop Thomas Tenison made him rector of Ruckinge, having previously allowed him to hold the small vicarage of Chislet 'in sequestration.'
He had up to this point taken the required oaths; but the attempts of his relation Jeffray Gilbert to bring him back to the Whig side had the opposite of the intended effect; and Henry Sacheverell's trial made him decide never to take the oath again. He published a sermon 'on the remission of sins,' in 1711, which gave offence by its view of sacerdotal absolution, and was attacked by Dr Robert Cannon in Convocation (22 February 1712). The proposed censure was dropped apparently by the action of Francis Atterbury as prolocutor. In a later sermon 'On the Honour of the Cnristian Priesthood' he disavowed a belief in auricular confession.