Thomas Rymer (c. 1643 – 13 December 1713) was an English antiquary and historian. His most lasting contribution was his compilation and publication of the Foedera, sixteen volumes of texts of agreements made between the crown of England and foreign powers during all earlier centuries. He held the office of English Historiographer Royal from 1692 to 1714.
Thomas Rymer was born at Appleton Wiske, near Northallerton in the North Riding of Yorkshire in 1643, or possibly at Yafforth. He was the younger son of Ralph Rymer, lord of the manor of Brafferton in Yorkshire, described by Clarendon as possessed of a good estate. The father was executed for his part in the Farnley Wood Plot of 1663. The son studied at Northallerton Grammar School where he was a class mate of George Hickes. Here he studied for eight years under Thomas Smelt, a noted Royalist. Aged sixteen, he then went to study at Sidney Sussex College, Cambridge, entering on 29 April 1659.
Although Rymer was still at Cambridge in 1662, when he contributed Latin verses to a university volume celebrating the marriage of Charles II and Catherine of Braganza, there is no record of his taking a degree. This may have been due to the financial problems his father was suffering at the time, or the fact that on 13 October 1663 his father was arrested, and executed the following year, for his involvement in the Farnley Wood Plot to stage an uprising in Yorkshire against King Charles II. Although Thomas's elder brother Ralph was also arrested and imprisoned, Thomas himself was not implicated, and on 2 May 1666, he became a member of Gray's Inn, and was called to the bar on 16 June 1673.