Robert Maitland O'Reilly (January 14, 1845 – November 3, 1912) was the 20th Surgeon General of the United States Army, serving from September 7, 1902 to January 14, 1909. O'Reilly was born in Philadelphia Pennsylvania to John and Ellen (Maitland) O'Reilly. He was a descendant of General Alexander O'Reilly who was a captain general of Cuba and one of the Spanish governors of Louisiana. The American branch settled in Pennsylvania before the American Revolution. O'Reilly was educated in the Public Schools of his native city.