Ronald James Thom, OC (May 15, 1923 - October 29, 1986) was a Canadian architect. He is well-known for two works: Massey College and Trent University's riverside campus.

He was born in Penticton, British Columbia and served as an aviator with the RCAF during World War II, returned and graduated from the Vancouver School of Art in 1947. He never went to architecture school but apprenticed at Thompson, Berwick & Pratt, where he quickly became recognized as an unusually gifted draughtsman and designer and also designed notable houses in the Vancouver area, several of which won Massey Awards, the country's top award for architecture. In 1957, he became a registered architect at Thompson, Berwick and Pratt and a partner shortly afterward.

He established R.J. Thom & Associates in Toronto in 1963 and later the Thom Partnership. He was a Fellow of the Royal Architectural Institute of Canada. In 1980, he was made an Officer of the Order of Canada. He battled alcoholism throughout his life and was eventually forced out of the partnership by some younger partners. He died at his office in 1986 after a bout of heavy drinking. His ashes were taken back by his family and scattered off the Pacific Ocean at Lighthouse Park in West Vancouver.

He was the subject of a major retrospective exhibition in 2013 and 2014, "Ron Thom and the Allied Arts" featuring a collection of photographs, drawings, letters and furniture that he designed for his buildings. The exhibition was shown in British Columbia in 2013, at the Gardiner Museum in Toronto beginning in February 2014, and at the Beaverbrook Gallery, Fredericton in November 2014.