Arumugam Ponnu Rajah (7 July 1911 – 28 September 1999), also known as A. P. Rajah, was a Singaporean judge, diplomat and politician who served as Speaker of the Parliament of Singapore between 1964 and 1966. Rajah also served as Singapore High Commissioner to the United Kingdom and later Singapore High Commissioner to Australia. He was Singapore's first Supreme Court judge to remain on the bench after turning 70.