Murdoch Mackay (April 30, 1884 – December 18, 1962) was a Manitoba politician. He led the Manitoba Liberal Party from 1931 to 1932, and brought the party into an alliance with John Bracken's Progressives. the son of John Mackay and Anna MacAulay. He subsequently moved to Manitoba, by 18 votes in the riding of Springfield.
The provincial Liberals fared poorly in this election, winning only seven seats in a 55-member legislature. Party leader Hugh Robson stepped down in 1930. After a brief period in which James Breakey led the parliamentary caucus, Mackay was chosen over Fred C. Hamilton as party leader in 1931.
MacKay brought the Manitoba Liberals into an alliance with the governing Progressives in 1932.
MacKay died at St. Boniface Hospital on December 18, 1962, and was buried at Transcona Cemetery.
MacKay had a great love of learning and, as such, Murdoch MacKay Collegiate, a high school in Winnipeg, was named in his honour