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 pioneering 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 from her career in 1999. Roberta Williams is one of the most influential PC game designers of the eighties and nineties, and has been credited with creating the graphic adventure genre.