William Mearns Sinclair (14 October 1934 – 2023) was a Scottish professional footballer who played as a midfielder for Aberdeen, Falkirk, Huddersfield Town, Tranmere Rovers, Halifax Town and Stirling Albion. In the early 1960s, Sinclair moved to Australia where he played for Adelaide Polonia and APIA. He later returned to Scotland, and lived in Fife, where he died in 2023, at the age of 89.