Six Flags Discovery Kingdom, Theme park in Vallejo, United States.

Six Flags Discovery Kingdom is a theme park in Vallejo, California, that unites roller coasters, water rides and animal enclosures on a wide site. The grounds divide into several zones where visitors move between rides and pools holding marine life.

Marine World opened in 1968 as a small zoo in Redwood City, California. In the mid-1970s it merged with the failing land-animal park Africa USA and became Marine World Africa USA. The park moved to its Vallejo site and opened there in 1986; the city of Vallejo took ownership in 1996 after the park defaulted on its debt. Premier Parks added rides, and the park joined the Six Flags chain in 1999, taking the name Six Flags Discovery Kingdom on 17 January 2007.

The park's name changed to Six Flags Discovery Kingdom on January 17, 2007, to reflect its three parts: land animals, sea life and rides, organised into Land, Sea and Sky zones. The 1999 Six Flags takeover brought Warner Bros.' Looney Tunes characters into the theming, and the children's area Popeye's Seaport was rebranded Looney Tunes Seaport.

The park opens longer in summer than in winter, with the main season running from late May to early September. Those wanting to shorten waiting times come best on weekdays outside school holidays.

The grounds hold sharks, giraffes, tigers and elephants beside fast roller coasters, so visitors switch from an aquarium to a loop within minutes. This combination exists at only a few sites worldwide.