James Chalmers McRuer, OC (August 23, 1890 – October 6, 1985) was a Canadian lawyer, judge, commissioner and author in Ontario.Born in Oxford County, Ontario, he received his law education from the Osgoode Hall Law School and was called to the Bar of Ontario in 1913. During World War I, he served in the Canadian Field Artillery as a Lieutenant. After the war, from 1921 to 1925 he was an Assistant Crown Attorney for Toronto and County of York.