Sierra Entertainment (formerly Sierra On-Line) was an American video game developer and publisher founded in 1979 as On-Line Systems by Ken and Roberta Williams. Based in Los Angeles, California, the company was last owned by Activision, a subsidiary of Activision Blizzard.
Sierra is best known today for its multiple lines of seminal graphic adventure games started in the 1980s, some of which proved influential in the history of video games (King´s Quest Series and Phantasmagoria). The Sierra label has been absorbed by its parent company. Some franchises which were published by Sierra will be published by Activision. Activision announced in 2008 that they may sell the Sierra brand.
In 2008, Sierra parent company Vivendi Games Universal, which had since been renamed Vivendi Games in 2006, merged with video game publisher Activision to form the Activision Blizzard holding company. Vivendi Games ceased to exist and ownership of Sierra was transferred over to Activision. Later that year, Sierra was closed down for possible future sale.