Jenson Button will return to Williams in 2021 as a senior advisor after the 2009 Formula 1 world champion signed a multi-year agreement with the team.
Button made his F1 debut with Williams in 2000, and would go on to score 15 race wins and win the world title with Brawn nine years later, before making his final grand prix start in 2017 with McLaren.
Button has remained involved in motorsport since leaving F1, focusing mainly on sportscar racing across Super GT and the World Endurance Championship, as well as backing a team in British GT.
He will now make an official return to F1 in the new role of senior advisor at Williams, as announced by the team on Friday.
Button will "provide advice and guidance to the team at Grove, along with helping support and develop both race and academy drivers," according to Williams, and will be on-site at a number of races with the team through 2021, as well as maintaining his punditry role for Sky Sports F1.
"I am so delighted to once again be able to say that I've signed for Williams," said Button.
"Back when I was 19 it was a moment that changed my life and, despite the fact it was over 20 years ago, I already feel like I never really left.
"Sir Frank Williams showed faith in me which I will be eternally grateful for and I am incredibly excited to have the chance to come back and help the team as it strives once more for success.
"There's a lot of hard work to be done but I have no doubt the future is incredibly bright for this fantastic team and I can't wait to get started."
The arrival of Button is the latest management change at Williams following the team's takeover by Dorilton Capital in August and the departure of the Williams family.
Simon Roberts has now taken up the role of team principal full-time, while former Volkswagen motorsport chief Jost Capito has become its new CEO.
"Bringing Jenson back on board is another positive step to help us move forward as a team both on and off track," said Capito.
"Jenson has always been a friend of the team and so it is great to welcome him back into the Williams family. Back in 2000, Sir Frank saw the promising talent Jenson had as a driver and gave him his first opportunity in F1.
"He more than fulfilled that initial promise throughout a glittering career that culminated in world championship glory.
"More recently, he has shown his acumen in both the business and broadcasting worlds and remains a widely respected figure in the paddock. All this experience will add another layer to our transformation both technically and as a business.
"I know everyone at Grove has huge respect for him and we're delighted to start working with him."