Raphael "Raph" Koster is an American entrepreneur, game designer, and author, known for his significant contributions to the online gaming industry. His career began with involvement in MUDs as a developer for Worlds of Carnage and implementor of LegendMUD in the early 1990s. In 1995, Koster joined Origin Systems, where he served as the lead designer for the seminal massively multiplayer online role-playing game (MMORPG) Ultima Online (1997) and Ultima Online: The Second Age (1998).