John Henry Denig (September 8, 1838 – December 10, 1876) was a United States Marine Corps sergeant serving aboard the USS Brooklyn during the American Civil War. He received the Medal of Honor for his actions in 1864 during the Battle of Mobile Bay. Denig died of health complications at age 38 and was buried in York's Prospect Hill Cemetery. He is one of two Medal of Honor recipients interred in the cemetery, the other being Charles H. Ilgenfritz.