Rory Kostjasyn (born 6 June 1987) is a former Ireland international rugby league footballer. He played in the National Rugby League for the Melbourne Storm and North Queensland Cowboys, with whom he was a member of their 2015 NRL premiership and 2016 World Club Challenge winning sides. An Ireland international and New South Wales Country representative, he played at hooker, but could also fill in at lock, and five-eighth. Kostjasyn currently works in the Newcastle Knights coaching department and previously coached their Canterbury Cup NSW team.
During pre-season training with the Knights on 7 January, Kostjasyn suffered an accidental blow to his throat from Danny Levi. He was required to be sent immediately to the John Hunter Hospital after suffering a fracture in the Cricoid cartilage in his neck. He stayed overnight in hospital and was released on 8 January. On 25 July, he announced his retirement from rugby league due to breathing difficulties from the injury.