Tadhg Furlong has signed a three-year IRFU contract to remain at Leinster until June 2021.
Furlong made his Ireland debut against Wales in the 2015 Guinness Summer Series before being named in the squad for the 2015 Rugby World Cup.
This year, the tighthead started every game of the RBS 6 Nations and has a total of 19 caps for Ireland.
The 25-year-old was selected for the 2017 British and Irish Lions squad, starting for all three Test matches against New Zealand.
"I am delighted to have signed a contract with the IRFU to continue to play with Leinster," Furlong said following the announcement.
3. It's The Magic Number for @tadhgfurlong as he signs a new three year IRFu deal to stay with @leinsterrugby #ShoulderToShoulder pic.twitter.com/2QX2WYlQfm
— Irish Rugby (@IrishRugby) December 15, 2017
"I got a number of opportunities over the past few seasons that have helped me to develop as a player and I want to continue to develop and be successful with both Leinster and Ireland."
A consistent player for Leinster, he has scored four tries and won 73 caps for the province since his debut in 2013.
Mick Dawson, CEO of Leinster Rugby commented: "His signature is a huge boost as we continue to build for the coming seasons.
"Securing home grown and young talent like Tadhg is a key part of the Leinster way."
The news will come as a relief following news of Simon Zebo’s departure to France and amid speculation about key players such as Peter O’Mahoney.