Ian Denys Turnbull (July 1, 1935 – November 21, 2025) was a politician in Manitoba, Canada. He was a New Democratic member of the Legislative Assembly of Manitoba from 1969 to 1977, and a member of Edward Schreyer's cabinet from 1973 to 1977.
The son of Matthew Turnbull, he received his B.A. and M.A from the University of Manitoba. In 1961, Turnbull married Aleda Winnifred Woodworth. In his career, he did research at the University of Manitoba, taught high school, and with his wife developed a consulting partnership with contracts mostly in Asia in addition to his involvement in politics. He was first elected to the Manitoba legislature in the provincial election of 1969, defeating Progressive Conservative incumbent Obie Baizley who was then Minister of Labour defeating Liberal June Westbury by 1598 votes. He was named Minister of Consumer, Corporate and Internal Services with responsibility for the Manitoba Telephone System and the Public Utilities Commission. He was also appointed Chair of the Management Committee of Cabinet. Following a cabinet shuffle on September 22, 1976, he was promoted to Minister of Education.
In the 1977 election, he lost to Tory candidate Gerald Mercier by 96 votes.