Six Nations Grand Slam winners Jonathan Davies, Ken Owens and Rob Evans have signed new contracts with Scarlets.
The Wales trio all came through the Scarlets academy and were part of the team that won the PRO12 in 2017.
Scarlets head coach Wayne Pivac, who will take over from Warren Gatland as Wales coach after the World Cup, said: "I am delighted that Rob, Ken and Jon have re-signed for the Scarlets.
"They have been a big part of our success in recent years and I know that our incoming coach Brad [Mooar] was very keen to secure their services moving forward.
"It is great news for the Scarlets."
British and Irish Lions centre Davies has made 154 appearances for the club, who he rejoined in 2016 after a stint in France with Clermont Auvergne.
"I am excited about the end of the season and having spoken to our new coach Brad, excited about what is to come," said the 30-year-old.
"It is something I want to be part of. You want to be playing in the big competitions and competing for trophies and we have been doing that at the Scarlets."
Owens was also a Lions tourist in 2017 and won his 64th cap for Wales in their Grand Slam-clinching win over Ireland.
The hooker has played 238 times for the club while prop Evans has made 118 appearances and was named in the PRO14 dream team last season.
"I want to keep playing for Wales and there is no other side in Wales I would want to play for," said Evans.
"This is an exciting time to be involved with the Scarlets. I am looking forward to pulling on a Scarlets jersey again and helping us get into the play-offs for another season."