Williams has not played a Test for Wales since the World Cup match against Portugal in September 2023.
“It is great to be back in the Wales set-up,” said Williams.
“I have been gutted to have missed a couple of squad selections, so I’m obviously delighted to be back in the mix.”
Following the departures of Jonathan Davies and Scott Williams, he is now the elder Scarlets statesman in a crop of centres that includes internationals Joe Roberts and Eddie James, with the uncapped Macs Page also selected for Wales’ tour of Japan.
“I have been here five years now and I feel this team is really evolving,” said Williams.
“There is a lot of talent within the squad, especially with the young guys coming through – I am one of the oldest players in the squad now at 28.
“These are exciting times and I am looking forward to seeing where this team can go.”
Fellow backs Page, James, Roberts, Tomi Lewis and Sam Costelow have also agreed new deals, alongside Wales forward duo Taine Plumtree and Kemsley Mathias.
New Scarlets signings include fly-half/centre Joe Hawkins, lock Jake Ball, scrum-half Dane Blacker and full-back Ioan Jones.
