Ian David Sinclair, OC QC (December 27, 1913 – April 7, 2006) was a Canadian lawyer, businessman, and senator. He was born in Winnipeg, Manitoba, and received a Bachelor of Arts degree in economics in 1937 from the University of Manitoba and a Bachelor of Law degree from the Manitoba Law School in 1941. Sinclair was called to Bar of Manitoba in 1941. From 1942 to 1943, he was a lecturer in torts at the University of Manitoba. In 1983, he was summoned to the Senate of Canada and represented the senatorial division of Halton, Ontario. A Liberal, he retired on September 27, 1988.