John Southby (1594–1683) was an English landowner and politician who sat in the House of Commons from 1654 to 1656.
Southby was the son of Richard Southby of Carswell Manor in the parish of Buckland in Berkshire (now Oxfordshire) and his wife, Jane, the daughter of Edward Keate of Lockinge in Berkshire (now Oxfordshire). His father died when he was twelve and he inherited the manor which he is considered responsible for rebuilding in the first half of the 17th century. He was a Justice of the Peace for Berkshire and was High Sheriff of Berkshire in 1647.
- 'Parishes: Buckland', A History of the County of Berkshire: Volume 4 (1924), pp. 453–460. Date accessed: 9 July 2011
- Willis, Browne (1750). Notitia Parliamentaria, Part II: A Series or Lists of the Representatives in the several Parliaments held from the Reformation 1541, to the Restoration 1660 ... London. pp. 229–239.
- W R Williams Parliamentary History of the County of Gloucester