The hotel group, Radisson SAS, has said it will create 1,000 new jobs in Ireland between now and 2007.
The hotel group said within the next few years it would open 10 new hotels in Ireland at various locations.
The group currently has four hotels with 650 rooms. The company did not disclose where all the hotels would be, but said there would be openings in Sligo, Letterkenny, Belfast and Athlone.
At present, the company is confined to Dublin, Galway, Limavaddy and Limerick. The announcement was made in the first hotel it opened in Ireland in Stillorgan on Dublin's southside.
The company said 5,000 indirect jobs in areas like outsourcing, servicing and supply chain management would also be created. As part of the expansion, a new brand, Park Inn, will be introduced.
The parent company of Radisson SAS is Rezidor SAS Hospitality. Mr Kurt Ritter, president and chief executive of that company, said it was constantly looking for "new market opportunities" and Ireland was one of those.
A statement said the company's ambition was to become the "premier hospitality company in Ireland".
It said concerns about the health of the tourist industry both at home and abroad had "in no way diminished the aggressive expansion plans" of the company.
The Tánaiste, Ms Harney, speaking at the announcement in Stillorgan, said the investment was a "strong vote of confidence in the future growth of Irish tourism".
"Tourists coming to Ireland now demand high standards and top-class service. I believe Radisson SAS has a proven track record which will ensure delivery of this service and further enhance Ireland's reputation," she said.