Sir Robert Ross McDonald QC (25 January 1888 – 25 March 1964) was an Australian politician who was a member of the Legislative Assembly of Western Australia from 1933 to 1950, representing the seat of West Perth.
He served as leader of the Nationalist Party from 1938 to 1945, and of the Liberal Party (its successor) from 1945 to 1946, during the period when those parties were the junior partners in the coalition with the Country Party.