Roberta Williams (born February 16, 1953) is an American video game designer, writer, and a co-founder of Sierra On-Line (later known as Sierra Entertainment), who developed her first game while living in Simi Valley, California. She is most famous for her work in the field of graphic adventure games with titles such as Mystery House, the King's Quest series, and Phantasmagoria. She is married to Ken Williams and retired in 1999. Roberta Williams was one of the most influential PC game designers of the 1980s and 1990s, and has been credited with creating the graphic adventure genre.