Irish people in search of home-holidays and short breaks now make up the largest group of people booking rooms through the reservation service for tourist board-approved accommodation.
Hotels have outstripped town centre B&Bs (known as townhouses) as the most booked accommodation.
The findings from Gulliver Ireland, the online and tourist office booking service, show that last year more than 130,000 hotel, B&B and guesthouse bookings, valued at €24 million, were made through Gulliver, now in its 10th year.
Seven years ago Irish people made up 19 per cent of those booking accommodation. Now they make up almost one-third of bookings and have replaced UK holidaymakers in the top position.
The share of UK tourists booking accommodation fell to 23 per cent last year. US tourists make up the third-largest group.
Set up by the then Bord Fáilte and the Northern Ireland Tourist Board, Gulliver is now wholly owned by financial services company Fexco in Co Kerry.
The internet had "revolutionised" how tourists and domestic holidaymakers book breaks and some 60 per cent of Gulliver bookings, valued at €17.6 million, are now made online, according to the company.
Ten years ago all Gulliver bookings for B&Bs, hotels and guesthouses and self-catering were made through tourism offices. The launch of the online booking platform seven years ago saw 4 per cent of bookings made online. Now only one-third of accommodation is reserved in tourism offices.
Stewart Stephens, the company's managing director, said hotel bookings now made up almost half of all tourism bookings through Gulliver, outstripping the key position once held by townhouse accommodation.
"This remarkable growth [from 16 per cent in 1997] is a function of phenomenal hotel development ... and the range, availability and value for money of hotel bedrooms," Dr Stephens said.
Three-star had been the most booked hotel grade every year and on average €56.17 was being paid per person sharing per night in this grade last year.
Five-star accommodation averaged €87.96 per person sharing.
The Dublin region continued to be the most booked in the country, accounting for 35 per cent of all reservations last year, followed by Galway at 14 per cent and Kerry at 10 per cent.