The budget carrier will add Split and Dubrovnik to its summer 2019 programme from Dublin.
Both routes will be operated twice-weekly.
Vincent Harrison, managing director Dublin airport, said: “These beautiful Croatian cities are full of culture and history and I have no doubt they will be hugely popular destinations.
“We will work close with Ryanair’s management team to promote its new services.”
Ryanair’s summer 2019 programme at Dublin will feature more than 100 routes, including 13 new ones, and more than 800 flights a week.
New destinations include Bodrum, Bordeaux, Bournemouth, Caligari, Dubrovnik, Frankfurt, Gothenburg, Kyiv, London Southend, Lourdes, Luxembourg, Split and Thessaloniki.