John Jeffreys
John Jeffreys may refer to:
- John R. F. Jeffreys, British mathematician and World War II codebreaker
- John Gwyn Jeffreys, British conchologist and malacologist
- J. G. Jeffreys, Australian schoolteacher who moved to England and founded Bryanston School in Dorset
- John Jeffreys (died 1689), British Member of Parliament for Brecon and Breconshire
- John Jeffreys (died 1715), British Member of Parliament for Breconshire, Marlborough and Radnorshire
- John Jeffreys (1706–1766), British Member of Parliament for Breconshire and Dartmouth