Kat Sadler is a British comedian, actress, and writer. Sadler was born in 1994 and is from Sutton, London. She has a younger sister, actress Lizzie Davidson. Sadler started in comedy at Warwick University where she studied film and literature. She would write sketches for the comedy society and performing stand up comedy. Sadler was a writer on The Mash Report and won the BBC Radio Comedy Writers Bursary in 2019. Her writing credits also include Joe Lycett's Got Your Back for Channel 4, The Jonathan Ross Show for ITV, Newsjack for BBC Radio 4 Extra and Frankie Boyle's New World Order for BBC Two, The Now Show and The News Quiz for BBC Radio 4, and Hypothetical and Mel Giedroyc: Unforgivable for Dave.

At the start of 2020, Sadler had deteriorating mental health, experiences she drew from for the BBC Three and Hulu sitcom Such Brave Girls (2023) which she wrote and starred in alongside her real life sister Lizzie Davidson. Discussing the 2021 pilot episode, Sadler said that "everything we joke about in the show is from a place of lived experience. I wish I could say this is a heart-warming show about overcoming trauma, but that would be a lie. It’s about three toxic, damaged egomaniacs manipulating the world and each other for their own personal gain, vengeance and glory…just like in Little Women." Upon the start of filming the series in 2023, Sadler described the show as “a family sitcom about trauma, but it’s more about us being narcissistic losers who are pathetically obsessed with what people think about us.