James O. McManus (born October 18, 1894) was an American politician. Between 1939 and 1941 he was lieutenant governor of the state of Rhode Island. James O. McManus was born in Philadelphia, a son of James and Mary (Hallinan) McManus. Both his parents were Irish immigrants. He received his early education in the public schools of Coventry, Kent County, and then attended the Warwick High School, after which he became a student at Bryant & Stratton’s Business College, Providence. From there he went to Georgetown University, attending its law school, from which he graduated with the degree of Bachelor of Laws in 1920. He was admitted to the Rhode Island bar in 1921.