Joe McCarthy has signed a three-year central contract that will keep him with Ireland and Leinster until the end of the 2027/28 season.
The 23-year-old second row has won 17 international caps since making his Test debut against Australia in 2022, and has played 42 times for Leinster.
The Dubliner, who stands 6ft 6in, and weighs over 17st, was a key part of Ireland's Guinness Six Nations-wining campaign in 2024 and becomes the youngest player on the IRFU's central contract system.
McCarthy said: "I am delighted to continue my association with Leinster and Ireland and I believe there’s a lot more to come as we build towards an exciting end to the season and beyond.
"I have loved playing for my home province and representing my country is a huge honour which means the world to me.
"I would like to thank my team-mates and coaches for their help and support and I have no doubt that there’s more to come as we collectively build towards the future."
IRFU Performance Director David Humphreys said: "Since making his provincial and international debuts three years ago, Joe has quickly established himself in the engine room of the Leinster and Ireland packs and we are delighted that he has agreed this new three-year deal.
"His application, physicality and talent has enhanced his reputation for club and country and it is a big statement for Irish rugby that one of the top young talents has committed his long-term future here.
"We all look forward to watching his continued progression over the years to come."
Earlier on Monday morning, the IRFU announced that Connacht and Ireland wing Mack Hansen had signed a two-year central contract.
Jamie Heaslip previews Ireland v France
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