"Girlfriend" is a song by Canadian pop-punk singer Avril Lavigne, released as the lead single from her third album, The Best Damn Thing.

It was produced by Lukasz Gottwald. "Girlfriend" became Lavigne's biggest hit in the United States, where it became her first number one single in the U.S. Billboard Hot 100. It topped the chart in Australia for 6 weeks, and reached number two in the United Kingdom. A remix featuring rapper Lil Mama was released in June 2007.

The music video is notable for being the 2nd most watched YouTube video of all time, with over 120 million views as of June 16, 2009 and also the most discussed music video.

The song involves Lavigne proclaiming a crush on a boy currently with his girlfriend and features the typical 80's pop-punk influence and power pop of her earlier songs. Lavigne said on the DVD side of the deluxe edition of The Best Damn Thing that in the bridge when the listener hears hand clapping, the accompanying giggling was created by Lavigne and Gottwald, despite it sounding like a girl.

"Girlfriend" is in the video game Burnout Dominator in English, Japanese, Spanish, and Chinese. It also appears in Burnout Paradise but this time only in English. This song is recorded in 7 languages other than English. It is the theme song of Japanese talk show Cartoon KAT-TUN - on which Lavigne appeared on May 2, 2007 - as well as being the insert song for popular Japanese manga based drama Hanazakari no Kimitachi e. It is featured in the theatrical trailer for the 2007 live-action Bratz film, and in a trailer for the film I Now Pronounce You Chuck and Larry, and also for Bring It On: In It to Win It.

Lavigne performed the song on The Tonight Show with Jay Leno on June 15, 2007. This song has rise anger in some of Lavigne's fans because of her change to a more feminine image.

(Wikipedia)