Fanning was born in Conyers, Georgia. She is the daughter of Heather Joy (née Arrington), and Steven J. Fanning. Her mother played tennis professionally and her father played minor league baseball for the St. Louis Cardinals. He is now an electronics salesman in Los Angeles, California. Her maternal grandfather is American football player Rick Arrington, and her aunt is ESPN reporter Jill Arrington. Fanning is the younger sister of Dakota Fanning, who is also an actress. Fanning has Irish, German, English, and French ancestry. Fanning and her family are members of the Southern Baptist Convention. Fanning currently attends Campbell Hall School in North Hollywood, Los Angeles.