Harriet Marston Slater (born 28 November 1994) is an English actress. On television, she is known for her roles in the DC Universe series Pennyworth (2019–2022) and the MGM+ period drama Belgravia: The Next Chapter (2024). She was named a 2023 Bright Young Thing by Tatler
Slater was born and raised in Leicester. Her extended family were active in amateur dramatics. She joined a local youth theatre group called the Little Theatre at the age of 6. She found acting a stress-reliever from anxiety. Slater has mentioned Lindsay Lohan and Jane Fonda as influences when young. She graduated with a Bachelor of Arts in Acting from the Guildford School of Acting in 2016.
After graduating from drama school, Slater immediately began her career in regional theatre, making her professional debut in The Man with the Hammer at the Theatre Royal, Plymouth in 2016. This was followed by a role in the 2017 Royal Shakespeare Company production of Phil Porter's Vice Versa at the Swan Theatre. She also appeared in The Secret Seven at Storyhouse.
