Ireland captain Rory Best and fullback Rob Kearney have signed new contracts with the Irish Rugby Football Union until the 2019 World Cup.
The pair are the only members of Joe Schmidt's squad to participate in the recent Grand Slam success -- sealed by Saturday's 24-15 victory over England at Twickenham -- and the clean sweep of 2009.
Best, who has amassed 111 caps, was at the helm throughout the Six Nations title run and has guided Ireland to their first victory over New Zealand and a maiden Test win against the Springboks in South Africa since taking over two years ago.
"I am in a very privileged position as captain of Ireland and Ulster to be involved with two groups of incredibly talented players," said Best, 35, who continues at the PRO14 outfit as part of the deal.
"I feel I can continue to make a contribution to both Ireland and Ulster and am delighted to have extended my contract to the next World Cup."
IRFU Performance Director, David Nucifora, added:"Rory has been an outstanding leader for Ireland and continues to produce stand-out performances at the highest level of the game.
"He is an important member of the Ireland leadership group and we are delighted that he will continue to play a central role in Irish Rugby."
Kearney has accumulated 83 caps since making his debut in 2007 and started every match of the 2018 campaign, culminating in an outstanding performance against England.
"I am delighted to have extended my IRFU contract and look forward to continuing to achieve with this Ireland squad," Leinster's double British & Irish Lions tourist said.
"There have been some fantastic days for both Ireland and Leinster over the course of my career and there is huge potential for growth in both squads as we look to build and develop and challenge for honours."
Meanwhile, Best's Ulster teammate Iain Henderson has also extended his deal with the IRFU and will remain with the province until at least June 2021.
The forward played in four of Ireland's Six Nations matches and has earned 38 caps for the national side since making his debut against South Africa in 2012
"The Irish rugby setup is one of the best in world rugby," said Henderson. "Since turning professional, I have been able to develop in an environment that has seen both provincial and national teams being part of some fantastic days and indeed some challenging times over the past seasons.
"As a proud Ulster man, I have always stated my desire to help Ulster secure lasting success and a legacy that mirrors that of our neighbouring provinces."
Elsewhere in the PRO14, Cardiff Blues have announced the appointment of John Mulvihill as their new head coach on a three-year contract.
The Australian, who has previously coached in Super Rugby with Western Force and Japan's Top League, will join the Welsh region at the start of next season.
"John will be the perfect fit," said Cardiff Blues chief executive Richard Holland. "He has an abundance of experience and a track record of bringing through young talent, which is very appealing given the age profile of our squad.
"He has played an instrumental role in the careers of numerous top-class internationals including David Pocock, Matt Giteau, James O'Connor and Drew Mitchell, who all speak very highly of him."