Greg Costikyan (born July 22, 1959, in New York City), sometimes known under the pseudonym "Designer X", is an American game designer and science fiction writer. Costikyan's career spans nearly all extant genres of gaming, including: hex-based wargames, role-playing games, boardgames, card games, computer games, online games and mobile games. Several of his games have won Origins Awards. He co-founded Manifesto Games, now out of business, with Johnny Wilson in 2005.