Tourism boom: Overseas visitor spending up nearly a fifth to €661m in 2015
An additional €661m was spent in Ireland compared with 2014, tourism authorities said.
The number of trips to the Republic also increased.
Tourism Minister Paschal Donohoe said: "Today's figures confirm that 2015 was an exceptional year not just in terms of overseas visit numbers but also the associated revenue which totalled over 4.2 billion euros.
"The good news is that we are aiming for even further growth in visit numbers and associated revenue in 2016 and a strong marketing campaign is already under way.
"Of course this being St Patrick's week, Tourism Ireland's Global Greening initiative is taking place across the world at a time when many people are planning their holidays, giving Ireland an unparalleled platform to encourage people to pay us a visit."
Spending in Ireland by overseas visitors for last year rose by 19% compared with 2014.
The data also shows that the number of trips to Ireland in the key target market of holidaymakers rose by 20%, while spending by holidaymakers was up 28% for 2015 when compared with 2014.