Peter Conover Hains Jr. (January 9, 1872 - February 5, 1955) was a United States Army captain convicted of killing his wife's lover. The case became a sensational murder trial in New York City in 1908. He was the son of Major General Peter Conover Hains and the father of Peter C. Hains III. Hains attended the United States Naval Academy from 1889 to 1893, but did not graduate. He was commissioned into the United States Army in July 1898 with the rank of second lieutenant, serving with the artillery and achieving the rank of captain in December 1902.