Sir Ralph Ellis "Robin" Brook (19 June 1908 – 25 October 1998) was a British merchant banker and a director of the Bank of England. He was knighted in the 1974 New Year Honours. His wife Helen Brook was founder of the Brook Advisory Centres.
As a fencer, he competed at the 1936 and 1948 Summer Olympics. In 1936, he won the sabre title at the British Fencing Championships.
The son of a surgeon, Brook was educated, through scholarships, at Eton College and subsequently at King's College, Cambridge, where he studied under Maynard Keynes, earning a double first in Economics.