Ada, Countess of Atholl (c. 1221–25 December 1266), was the daughter and heir of Forbhlaith, Countess of Atholl and her husband, David de Hastings.
Ada's mother, Forbhlaith, was herself heir of the highland mormaerdom of Atholl, Scotland.
[1] Ada was Countess of Atholl suo jure, she held the title in her own right, and not through her husband.
She inherited the title from her mother, who was also suo jure Countess of Atholl.
David's father John was able to use the title of Earl but held it only by right of his wife, Ada, he was jure uxoris Earl of Atholl, as Ada's father had been.