"Complicated" is the debut single by Canadian singer-songwriter Avril Lavigne, released in 2002 from her debut album, Let Go. It was written by Lavigne and The Matrix (Scott Spock, Lauren Christy, and Graham Edwards), and produced by The Matrix. The single reached number one in Australia (for six weeks), New Zealand and Mexico (for nine weeks), number two on the Billboard Hot 100, behind "Hot in Herre" by Nelly and number three in the United Kingdom. Based on its chart performance, the song is Lavigne's second most successful single (only behind her 2007 single "Girlfriend") and was one of the most successful releases of 2002. Lavigne broke a record set by Natalie Imbruglia's "Torn" when "Complicated" held the number one spot on the Adult Top 40 chart for 16 weeks in a row. "Complicated" was nominated for two Grammy Awards for Song of the Year and Best Female Pop Vocal Performance.

After being signed to Arista Records in November 2000 upon the authorization of the label's CEO, Antonio "L.A." Reid, Lavigne moved to New York with the assistance of Reid. There, she began working on her debut album, Let Go, collaborating with a host of prime songwriters and producers. For six months, the label set up Lavigne with two co-writers, who worked with her upon Arista's instructions. Reid expected Lavigne to record folk songs because she auditioned to them in a "balladic, 'new country'" type. However, the collective failed to click "with a girl who'd just discovered guitar-based rock". For a year, nothing was working for Lavigne and was on the verge of getting dropped off Arista. The management pitched her songs written by other songwriters, but she declined, insisting she wanted to write songs herself. Lavigne relocated to Los Angeles, where she collaborated with songwriter-producer Clif Magness, who gave her ample creative control in the writing process. Lavigne and Magness wrote "Losing Grip" and "Unwanted", songs that she deemed reflective of her vision for the entire album. However, Arista was not thrilled with the heavy-guitar laden songs that Lavigne was writing, prompting the label to look for other producers to match their demands.

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