The low-cost airline will launch a service between Prestwick and Knock in Ireland from April next year. Flights will operate three times a week, on Wednesdays, Fridays and Sundays.
It comes weeks after the Scottish Government announced it was entering negotiations to buy the loss-making airport from New Zealand owner, Infratil.
However, Ryanair said the decision to launch the Prestwick-Knock route was a direct response to the announcement by the Irish Government, on October 21, that it would scrap the country's €3 air travel tax in April 2014.
Prestwick's passenger development manager Paula Horne said it was a "great vote of confidence in the airport's future".