Christie was born in 1978 in Sussex, England. From a young age she regularly participated in dance and gymnastics, which was a great introduction to her education in Drama school. However, after a serious injury, she moved into acting. She graduated in 2005 and started her acting career initially through theatre. Christie's first film debut was in 2007 for a short film by Nathaniel Mellors, she has then gone on to feature in many internationally recognised TV series and movies.
In 2011, Christie took part in the largely popular Game of Thrones franchise as Brienne of Tarth. For the role, Christie undertook both a new weight lifting routine, along with stage fighting lessons to immerse herself in the role.
Christie is recognised for her part as Captain Phasma, in the legendary film series Star Wars, co-starring in Star Wars: The Force Awakens and Star Wars: The Last Jedi.