Harthill will be responsible for developing partnerships for the property's accommodation, golf, food and beverage, country pursuits and spa activities and will report directly to director of sales and marketing Stephen Walker.
She has more than ten years experience in sales and marketing roles at the Sheraton Grand Hotel & Spa in Edinburgh.
Harthill said: "I'm delighted to join the sales and marketing team at Turnberry, especially now that developing partnerships and creating our own customer events has become a key part of the strategy. The recent renovation of the hotel and introduction of the sumptuous Turnberry Suite will allow us to provide the highest quality facilities for corporate groups and individual guests."
Turnberry was relaunched last July following a multimillion pound renovation programme.
It offers 198 rooms and ten meeting rooms with capacity for 220 delegates.