Sullivan turned professional in 2011; He secured his place on the European Tour for 2013 at the
2012 qualifying school. In 2013, Sullivan finished 98th on the Race to Dubai with his best finish being a tie for third at the
Alfred Dunhill Championship. In 2014, Sullivan finished 33rd on the Race to Dubai including a second-place finishing at the
Trophée Hassan II, a third place at the
KLM Open, and three more top-10 placements. During that season, Sullivan hit a hole-in-one at the
KLM Open earning him a flight into space. Sullivan's first European Tour win came in January 2015 at the
South African Open. Sullivan won the event in a playoff against South African
Charl Schwartzel who had started the final round seven strokes ahead of Sullivan. Sullivan quickly followed this success with wins at the 2015
Joburg Open in March and the
Portugal Masters in October, which was a wire-to-wire victory by nine strokes. He became the first man to record three victories on the European Tour in 2015, finishing with an 8th place in the final Order of Merit . In February 2016, he advanced to a career best 28th in the
Official World Golf Ranking. Thanks to his results on the 2015 and 2016 seasons of the European Tour he obtained an automatic selection for the
2016 Ryder Cup. In August 2020, Sullivan secured his first victory in five years at the
English Championship, a new event created as part of a UK Swing after the European Tour reorganised the
2020 season due to the
COVID-19 pandemic. His score of 257 over 72 holes was at the time the lowest score in a European Tour tournament on European soil, beating the previous best of 258, shared by
David Llewellyn in 1988 and
Ian Woosnam in 1990. ==Amateur wins==