"Girlfriend" is a popular song by Avril Lavigne written in the key of F major. It was released as the lead single from her third studio album, "The Best Damn Thing," in 2007. The song was composed by Lavigne, Lukasz Gottwald, and Aami Nij, and produced by Gottwald. Fun fact: the song's distinctive opening guitar riff is influenced by the song "Black Sabbath" by Black Sabbath. "Girlfriend" features energetic pop-rock elements and catchy hooks, making it one of Lavigne's most successful and recognizable songs.