"Fat Lip" is a song by the CanadianrockbandSum 41. It is the fourth track on their 2001 albumAll Killer No Filler and was released as the lead single in April 2001. It is the band's most successful single to date, topping theBillboardModern Rock Trackschart. It peaked at number 66 on theBillboardHot 100chart and at number 8 on theUK Singles Chart.