The Ansari X Prize was a space competition in which the X Prize Foundation offered a US$10,000,000 prize for the first non-government organization to launch a reusable crewed spacecraft into space twice within two weeks. It was modeled after early 20th-century aviation prizes, and aimed to spur development of low-cost spaceflight.Created in May 1996 and initially called just the "X Prize", it was renamed the "Ansari X Prize" on May 6, 2004 following a multimillion-dollar donation from entrepreneurs Anousheh Ansari and Amir Ansari.

The prize was won on October 4, 2004, the 47th anniversary of the Sputnik 1 launch, by the Tier One project designed by Burt Rutan and financed by Microsoft co-founder Paul Allen, using the experimental spaceplane SpaceShipOne. $10 million was awarded to the winner, and more than $100 million was invested in new technologies in pursuit of the prize.Several other X Prizes have since been announced by the X Prize Foundation, promoting further development in space exploration and other technological fields.

Elbert Leander "Burt" Rutan (; born June 17, 1943) is a retired American aerospace engineer and entrepreneur noted for his originality in designing light, strong, unusual-looking, and energy-efficient air and space craft. He designed the record-breaking Voyager, which in 1986 was the first plane to fly around the world without stopping or refueling, and the Virgin Atlantic GlobalFlyer, which in 2006 set the world record for the fastest (342 mph/551 km/h in 67 hours) and longest (25,766 miles/41,466 km) nonstop non-refueled circumnavigation flight in history. In 2004, Rutan's sub-orbital spaceplane design SpaceShipOne became the first privately funded spacecraft to enter the realm of space, winning the Ansari X-Prize that year for achieving the feat twice within a two-week period.

With his VariEze and Long-EZ designs, which first flew in 1975 and 1979 respectively, Rutan is responsible for helping popularize both the canard configuration and the use of moldless composite construction in the homebuilt aircraft industry, the latter a technique that was adopted in several production and commercial aircraft in the following decades as well. He is the founder or co-founder of multiple aerospace companies, including the Rutan Aircraft Factory, Scaled Composites, Mojave Aerospace Ventures, and The Spaceship Company.

Rutan has designed 46 aircraft throughout his career, been included in the Time 100 Most Influential People in the World list for the year 2004, been the co-recipient of both the Collier and National Air and Space Museum trophies on two occasions (each for his accomplishments with Voyager in 1986 and SpaceShipOne in 2004), received six honorary doctoral degrees, and has won over 100 different awards for aerospace design and development. In 1995, he was inducted into the National Aviation Hall of Fame. Rutan has five aircraft on display in the National Air and Space Museum in Washington, D.C.: the VariEze, Quickie, Voyager, SpaceShipOne, and the Virgin Atlantic GlobalFlyer. He is the younger brother of former test pilot and United States Air Force fighter pilot, Dick Rutan, who has piloted many of his earlier original designs on class record-breaking flights.