James Davies Lewin (April 1, 1812 – March 11, 1900) was a Canadian office holder, businessman, and politician.

Born in Womaston, Radnorshire (now Powys), Wales, the son of Samuel Lewin and Mary Furmage, Lewin was educated at the Kingston Grammar School, Wales.

He entered the British government service in 1830 and assigned to the customs department on the Miramichi River, New Brunswick.

In 1855, he was elected to the Presidency of the Bank of New Brunswick, and held this position until his death.

He was appointed to the Senate on the advice of Alexander Mackenzie on November 10, 1876, representing the senatorial division of St. John (Lancaster), New Brunswick.