Sophie Belinda Turner was born in England on 21 February 1996, the daughter of Sally, a nursery school teacher, and Andrew, who works for a pallet distribution company. She moved to Chesterton, Warwickshire when she was 2 years old. She attended Warwick Prep School until she was 11, and later attended the independent The King's High School for Girls. Turner has been a member of the theatre company Playbox Theatre Company since she was 3 years old. She has two older brothers. Her twin died before birth.