She has three older brothers, and is a granddaughter of the novelist and MI6 officer Alexander Wilson, and of his third wife, Alison (McKelvie).
Wilson grew up in Shepperton, Surrey,and was raised Catholic.
Wilson attended Notre Dame School and sixth form at Esher College. As a teenager, Wilson worked as a model, and went on to study history at the University of Nottingham, graduating in 2003. While at Nottingham, she was also involved in student drama at New Theatre (Nottingham).
She graduated from the London Academy of Music and Dramatic Art in July 2005. Afterwards, she co-founded Hush Productions.
During her time at Nottingham she participated in the TV war strategy game Time Commanders, helping her team mates fight in the Battle of Pharsalus.
Wilson is a two-time Olivier Award winner, and was nominated for a BAFTA and Golden Globe for Best Actress in a mini-series for her role in Jane Eyre as well as for a Satellite Award and won a Golden Globe for her role in The Affair.