William (foaled 1811) was a British Thoroughbred racehorse best known for winning the classic St Leger Stakes in 1814. In a racing career which lasted from May 1813 until May 1815 he contested eight races and won four times. After winning his last two starts as a two-year-old, he fell on his first appearance of 1814 and was beaten in his next race before winning the St Leger at odds of 7/1. He was beaten in his only race as a four-year-old and was sold and gelded before returning for two unsuccessful efforts in 1817.