Robert Spelman Robertson (December 11, 1870 – May 28, 1955) was a Canadian lawyer and judge. He was Chief Justice of Ontario from 1938 to 1952. Born in Goderich, Ontario, Robertson was called to the Bar in 1894. He entered private practice, first in Stratford, Ontario, until he was recruited by Fasken in Toronto in 1917. He was a prominent civil litigator, and was one of William Lyon Mackenzie King's favourite litigators in constitutional cases.