Katy Perry was born Katheryn Elizabeth Hudson in Santa Barbara, California. The second child of two pastors, she has an older sister and younger brother. Her Evangelical mother, Mary Hudson (nee Perry), grew up in Southern California and had "a tempestuous first marriage in Zimbabwe". Her father was a West Coast scenester in the 1960s. Perry's maternal aunt and uncle were screenwriter Eleanor Perry and director Frank Perry, through whom she is also related to Charles M. Schwab, the founder of the Bethlehem Steel Corporation. Perry is of Portuguese and German ancestry on her mother's side.

Katy was incorporated to her parents' ministry; she sang in their church from ages 9 to 17. Perry grew up listening to gospel music and was not allowed to listen to what her mother called secular music. Katy attended Christian schools and camps. As a child, Perry learned how to dance in a recreation building in Santa Barbara. Girl was taught by seasoned dancers and began with swing, Lindy Hop, and jitterbug.

Perry took her GED after her freshman year of high school and decided to leave school to pursue a career in music. Perry initially started singing "because I was at that point in my childhood where I was copycatting my sister and everything she did." Her sister practiced with cassette tapes, and Perry took the tapes herself when her sister was not around. Perry rehearsed the songs and performed it to her parents, who suggested she should take voice lessons. She grabbed the opportunity and began taking lessons at age nine to 16. Perry enrolled in at the Music Academy of the West in Santa Barbara, and studied Itaan opera for a short time.