William Gwyn Hullin (2 January 1942 - 3 October 2012) was a Welsh international rugby union scrum-half who played club rugby for Cardiff and London Welsh. He represented the Barbarians and played county rugby for Surrey and the London Counties. Hullin was capped only once for Wales, being unfortunate to be playing at the same time as Gareth Edwards, one of the greatest scrum-halves in world rugby. Despite his lack of international caps, he was a regular first team club player, and toured overseas, with Cardiff, London Welsh and the Barbarians. He was also a successful Sevens player, finishing in the winning team in both the Snelling Sevens and the Middlesex Sevens.