Born in Napanee, Ontario to conservative parents, Lavigne grew up singing country music and in a church choir and taught herself guitar. She was discovered by her first professional manager while singing country covers at a Chapters bookstore in Kingston, Ontario. By the age of 16, she was signed by Arista Records head L.A. Reid, and she subsequently moved to New York City to work on her first album.

Apparently, early attempts to co-write songs for her failed to meet her approval, and she eventually moved to Los Angeles, California and co-wrote her album with Clif Magness and songwriting team The Matrix, whose previous work included songs for Sheena Easton and Christina Aguilera. Her first album, Let Go, was released by Arista on June 4, 2002, and was certified "Quadruple Platinum" less than six months later by the Recording Industry Association of America. She was named "Best New Artist" at the 2002 MTV Video Music Awards and at the 2003 Juno Awards, where she led all musicians with six nominations, winning four Junos. She also has been nominated for eight Grammy Awards but has not won any to date.

As of June 2004, Let Go had sold 14 million albums and reached the number one spot in the United Kingdom, Australia and Canada and #2 in the US. In the U.K., Lavigne was the youngest female artist ever to have a number one album, although this record was later broken by Joss Stone. Also, Avril is the youngest Canadian to ever sell a million copies in Canada. Let Go spawned 5 hit singles (the first 3 with The Matrix), in various parts of the world.

The media has often compared her to Alanis Morissette, though she has been criticized for not being as strong a lyricist as Morissette at the same age. She has also often been compared with singers like Vanessa Carlton and Michelle Branch, who emerged at about the same time and were popularly credited, with Lavigne, as part of a trend towards more earnestness and genuine creativity in an often vacuous and pre-fabricated teen pop music market.

While her marketing has been every bit as sophisticated as, for instance, that of Britney Spears and her competitors, a profile in the Washington Post found that in the flesh, her personality reflected the marketing and found her, if anything, something of a wide-eyed innocent, citing the fact that she was intending to purchase her first Ramones CD. In another interview, she listed her current listening tastes as including Blink 182, Sum 41, and System of a Down. Lavigne had a close friendship with Deryck Whibley of Sum 41 and hired a former member of that band Mark Spicoluk as a member of her backing band. She describes her first album as a pop album with "a couple of rock songs on it," and has indicated a desire to write more rock-oriented songs in the future.