Jenson Button has returned to Williams in a senior advisory role after agreeing a multi-year deal.
Button was given his Formula One break by Williams 21 years ago when he was handed a drive for the 2000 season.
The 41-year-old Briton went on to be crowned F1 world champion during his time with Brawn in 2009 and retired in 2016 with 15 race victories to his name.
Button now returns to Williams, who were sold to American private investment firm Dorilton Capital last year as the Williams family ended their 43-year-old involvement in F1.
He will be tasked with passing on his experience at grands prix, while also attending team events in the United Kingdom.
Englishman Button said: "I am so delighted to once again be able to say that I've signed for Williams. 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."
Incoming Williams Racing chief executive Jost Capito said: "Bringing Jenson back on board is another positive step to help us move forward as a team both on and off track. 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."