James Robert Mann was an American politician and attorney who served as a member of the United States House of Representatives from Illinois from 1897 to 1922. He was a member of the Republican Party, and served as House Minority Leader from 1911 to 1919.

Party leaders of the United States House of Representatives, also known as floor leaders, are congresspeople who coordinate legislative initiatives and serve as the chief spokespersons for their parties on the House floor. These leaders are elected every two years in secret balloting of their party caucuses or conferences: the House Democratic Caucus and the House Republican Conference. Depending on which party is in power, one party leader serves as majority leader and the other as minority leader.