Doctor John Colin Gregory (28 July 1903 – 10 January 1959) was an amateur British tennis player, best remembered for winning the Australian Open in 1929. Gregory was born in 1903 in Beverley, Yorkshire, the son of Dr William Herbert and Constance Gregory. Like his father, he became a medical doctor but was also a successful amateur lawn tennis player in both doubles and singles. Gregory also played cricket, golf, rugby and squash. In the 1920s he played doubles with Ian Collins and they were runners up at the 1929 Wimbledon Championships. In 1929 he won the Australian singles championship.