Kenny will be joined by Beatrice Tollman, president and founder of Red Carnation Hotels, to launch the 82-bedroom hotel on the shores of Lough Corrib and the River Cong in County Mayo.
The restoration of the 787-year-old castle has included the addition of a 32-seat cinema, billiard room, cigar terrace, luxury lakeside cottage and a children's games room. A spa, featuring five treatment rooms, indoor ozone-filtrated swimming pool and Techno Gym, will open in July 2015.
Existing guest rooms at the hotel have been enhanced and decorated with antiques, original artwork and bespoke carpets.
Located within 350 acres of land, the hotel boats a number of outdoor facilities, including falconry, an equestrian centre, clay shooting, a nine-hole golf course, tennis, cycling, fishing and water sports.
The staff, headed by general manager Niall Rochford, has increased in number from 215 to 300 to support the improved facilities at the hotel.
Jonathan Raggett, managing director of Red Carnation Hotels, said: "Ashford Castle reopens as the jewel in our collection and certainly one of Europe's finest luxury hotels."
The hotel, which was bought by Red Carnation from Irish developer Gerry Barrett for £21.4m in 2013, is now part of a 17-strong portfolio of properties in the UK, Ireland, South Africa, Switzerland, and the USA.