Songfacts®:

• In a video interview posted on her website, Britney Spears explained this song. She said: "It's about me as an entertainer - what I do, and what I bring to a show, is basically like a circus. I bring costumes and fun theatrical things that make people in awe."
• This song was written and produced by Dr. Luke and Benny Blanco. Dr. Luke was also responsible for co-writing and producing both "I Kissed a Girl" and "Hot n Cold" for Katy Perry. Benny Blanco provided additional production on both songs.
• Spears explained that the album's title has a double-edged meaning. It refers to both her life being a metaphorical circus, and also her fondness for the actual big-top show. She said: "I like the fact that you're always on the edge of your seat when you're at a circus... You're never bored. You're just really engulfed in what's going on around you. And you want to know what's going to happen next."
• This went straight in at #3 in the Hot 100, making it the highest debuting single of Spears' career. Her previous best had been her first chart entry "…Baby One More Time," which opened at #17 in 1998.
  
  "Circus'" high new entry was bested by "3" and "Hold It Against Me," which both debuted at #1.
• The song was not only the title track of Spears' sixth album but also inspired the supporting tour. Co-writer Claude Kelly told AOL, "It's like a songwriter's dream in a lot of ways because for a songwriter everything starts with an idea for [the artist's] life and what I had known." He continued: "I didn't know her personally when I wrote it, but I read about her and saw that her life was like a circus. It was an idea I had on a plane. And to watch that idea turn into a song is a pleasure in itself. Then getting to see that song played to a big audience is a bonus. Then to watch the snowball affect, you can never really expect that. But when it does, it really shows you how far one idea can go. And that's what's inspired me in so many ways in my career that a small idea I thought of on a plane that was I wasn't sure about can blow up to this. It's an honor."