Perry was born in Santa Barbara, California, USA. The middle child of two pastors, she grew up listening to gospel music and singing in church. In her teenage years, Perry found a Queen record, "and the heavens opened and saved me. From then on, they have been my biggest influence," she said. In an article for Blender Magazine, Perry stated she wasn't "a typical Christian", mentioning that she had done a "lot of bad things" during her adolescence. Among her musical influences are Queen, The Beach Boys, Heart, Joni Mitchell, Paul Simon, and Alanis Morissette.

In her early career she toured churches and released a gospel album in the U.S. under the name Katy Hudson.

At the age of 17, Perry began working with legendary producer and songwriter Glen Ballard. Her songs captured the attention of Virgin Records CEO Jason Flom, the head of Capitol Music Group. Katy Perry was signed to Capitol Music in Spring of 2007. She was named Blender's "Next Big Thing" in October 2004 and Teen People's "One to Watch."

After signing to Capitol Records, Perry began recording for her official mainstream debut album, released in 2008, working with Cathy Dennis, Greg Wells, Dr. Luke, Butch Walker, Max Martin, Dave Stewart and Ted Bruner. The full-length album, titled One of the Boys, was released in the USA on June 17, 2008.Perry was an act in the 2008 Vans Warped Tour to promote the album.

The album was preceded by a digital EP in late 2007, entitled "Ur So Gay," produced by and co-written with Greg Wells (OneRepublic, Mika). A video for the song premiered in early 2008 and brought Perry to the attention of Madonna, who mentioned her on KISS FM and KRQ's JohnJay & Rich morning show in Arizona, stating that "Ur So Gay" was her "favorite song right now,"as well as another mention on Ryan Seacrest's Morning Show. "Ur So Gay" has been criticized for alleged homophobia.

On April 29, 2008, her first official single from One of the Boys, "I Kissed a Girl", debuted on the iTunes Store. The song debuted on the Billboard Hot 100 at #76, climbing to #1 as of June 25, 2008. It has peaked on iTunes Top 100 at #1, as of June 3, 2008. The music video for "I Kissed a Girl" was released on May 21, 2008, on MySpace. An essay in Slant Magazine argues that the song "isn't problematic because it promotes homosexuality, but because its' appropriation of the gay identity exists for the sole purpose of garnering attention—both from Perry's boyfriend and her audience."

As an actress, she made a cameo appearance in Carbon Leaf's video "Learn to Fly" and in Gym Class Heroes' video "Cupid's Chokehold." On March 10, 2008, she appeared as herself on ABC Family's "Wildfire" (episode titled "Life's Too Short"). She also has appeared in advertisements for 'Too Faced Cosmetics' Spring 2007 line.