Merlyn Rees, Baron Merlyn-Rees, PC (born 1920), was a British Labour party Member of Parliament from 1963 until 1992. In that year, he was created a Baron and entered the House of Lords.

He was Secretary of State for Northern Ireland from March 1974 until September 1976, when he moved back to London to become Home Secretary. For two years before the Labour government came to power in 1974 he had been Labour Party spokesman on Northern Ireland.

Rees wrote of his views on Northern Ireland in: Northern Ireland: a personal perspective (Methuen, London, 1985)

He is president of the Video Standards Council and Chancellor of the University of Glamorgan.

|- style="text-align: center;" | width="30%" |Preceded by:
Roy Jenkins | width="40%" style="text-align: center;" |Home Secretary
1976–1979 | width="30%" |Succeeded by:
William Whitelaw