The team were bought by US investment firm Dorilton Capital last year, in a move that led to founder Sir Frank Williams and his daughter Claire stepping down from their leadership roles.
Simon Roberts was appointed interim Team Principal following that move – an appointement that has since been made permanent, while ex-McLaren boss Jost Capito has been appointed CEO of the company.
And on Friday the team announced that 2009 World Champion Button, who drove for Williams as a 20-year-old F1 rookie in 2000, is rejoining on a multi-year agreement.
“As part of his role at Williams, Jenson will be able to call upon his over 30 years of motorsport experience to provide advice and guidance to the team at Grove, along with helping support and develop both race and academy drivers,” the team said.
Throughout the 2021 season, Button – who won the title with Brawn GP, and also raced in F1 for Benetton, Honda and McLaren – will attend a number of Grands Prix with Williams, take part in some team events in the UK, and will also support Williams’ media and marketing activities. He will combine this role with his media duties with broadcaster Sky Sports F1.
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.
“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.”
Jost Capito, incoming CEO of Williams, added: “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. 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.”