Underwood grew up in Oklahoma on her family's farm in Checotah. She started singing at a young age, initially at church and later in school plays and talent shows. In 2002 she entered Northeastern State University in Tahlequah, Okla., with intentions to pursue a career in broadcast journalism. Two years later she interrupted her studies to audition for American Idol. Underwood made the cut and ultimately won the competition after being chosen as the favourite by viewers. She received the top prize of a recording contract with 19 Recordings/Arista Records, and the resulting album, Some Hearts (2005), was a massive commercial success, selling some six million copies and cementing Underwood's status as one of American Idol's most successful alumni. She supported the album with a 150-show tour in 2006, sharing bills with Kenny Chesney and Brad Paisley in addition to headlining her own dates. Underwood made time to return to school, however, and in 2006 she graduated magna cum laude with a B.A. in mass communications from Northeastern State University. That same year she won best new artist and best female country vocal performance at the Grammy Awards (Grammy Award).

In April 2007 Underwood returned to American Idol, performing a cover of the Pretenders' "I'll Stand By You." Made available as a single on Apple's iTunes service, the song was downloaded more than 300,000 times and became the first digital-only release to crack the Billboard top 10. At the 2007 Country Music Association Awards, Underwood repeated her win (she had won in 2006) as female vocalist of the year and claimed single-of-the-year honours for "Before He Cheats." In 2007 she also released her second album, Carnival Ride, which sold more than half a million copies in its first week of release. The following year Underwood was inducted as a member of the Grand Ole Opry, joining the ranks of top country music artists such as Garth Brooks, Trisha Yearwood, and Martina McBride.