Sonnyboyliston (foaled 5 March 2017) is an Irish Thoroughbred racehorse. He made no impact as a two-year-old and was gelded before returning in 2020 to win three handicap races. He improved to become a top-class stayer as a four-year-old in 2021, winning the Martin Molony Stakes, Ebor Handicap and Irish St Leger.