Florence Leontine Mary Welch was born in Camberwell, London on 28 August 1986. Her father is Nick Russell Welch, an advertising executive. Her mother, Evelyn Welch (nee Evelyn Kathleen Samuels), is an American emigrant from New York City who was educated at Harvard University and the Warburg Institute, University of London. Evelyn is currently Professor of Renaissance Studies and Vice-Principal for Arts and Sciences at King's College London.

During interviews, Welch has cited Grace Slick and Alanis Morissette as influences and "heroes." She listed in her early influences the likes of John Cale, Siouxsie, David Byrne, Lou Reed, In a review of Ceremonials, Jody Rosen of Rolling Stone described Florence and the Machine's style as "dark, robust and romantic", deeming the ballad "Only If for a Night" as a mix of "classic soul and midnight-on-the-moors English art rock". Welch stated that her lyrics related to Renaissance artists : "We're dealing with all of the same things they did : love and death, time and pain, heaven and hell". Welch has used religious imagery in her music and performances, though she has stated "I'm not a religious person. Sex, violence, love, death, are the topics that I'm constantly wrestling with, it's all connected back to religion."  Nick Welch, her father, contributed a "rock and roll element to the family mix"; in his twenties, he lived in a West End squat and attended the Squatters' Ball organised by Heathcote Williams where The 101ers played regularly. A self-confessed "frustrated performer", if Nick, as he put it, "nudged Flo in any way, it's only been to listen to the Ramones rather than Green Day". Evelyn had an equally strong yet completely different influence on her daughter. A visit to one of her mother's lectures left teenage Florence deeply impressed. She explained, "I aspire to something like that but with music. I hope that my music has some of the big themes--sex, death, love, violence--that will still be part of the human story in 200 years' time".  Welch has stated she is an avid reader, and has been influenced by authors such as Gwendoline Riley, Kirsten Reed and David Vann. The art of literature is important to her. She actively participates in a fan run book club, 'Between Two Books'. Every few months, she will recommend a book to the club which they will read collectively. Welch enjoys poetry, and has mentioned that the poet Ted Hughes was a big influence on her first album, 'Lungs'.

What else did she use
I'm not a religious person. Sex, violence, love, death, are the topics that I'm constantly wrestling with, it's all connected back to religion."