Монтрёй
Haenel was born on 11 February 1989 in Paris. Her mother is a teacher and her father is a translator. She grew up in Montreuil, Seine-Saint-Denis in what she described as "a very left-wing, artistic neighborhood". She has Austrian heritage through her father and speaks fluent German. Haenel started acting at the age of 5 and was involved in local theatre. As a child, Haenel would mimic cartoon characters, particularly the characters of Tex Avery.