"Circus" is a song by American pop singer Britney Spears. The song was written and produced by Dr. Luke and Benny Blanco for Spears' sixth studio album of the same name.

The song was announced as the second single by Spears' official website on October 31, 2008 and released as the album's second single in late 2008. The single became Spears' first top-three debut on the Billboard Hot 100.