Peter J. Muldoon (October 10, 1863 – October 8, 1927) was an American prelate of the Roman Catholic Church. He served as the first bishop of the new Diocese of Rockford in Illinois from 1908 until his death in 1927. He previously served as an auxiliary bishop of the Archdiocese of Chicago in Illinois from 1901 to 1908. Muldoon served as chair of the National Catholic War Council during World War I and was a leader of the National Catholic Welfare Council during the 1920s.