Mercedes' director of strategy, James Vowles, will join Williams as team principal on Feb. 20, filling the vacant position left by Jost Capito last month.
Vowles is best known for his role in race strategies at Mercedes, including occasional messages to the drivers over team radio explaining decisions on the pit wall. However, he stood back from hands-on involvement in strategy decisions midway through 2022 to work in a wider managerial role and had long been tasked with overseeing its young driver programme.
He comes to Williams with two decades of experience in F1 and extensive knowledge of Mercedes, having spent his career working at the Brackley-based team through several different ownerships as far back as its time as British American Racing.
"I cannot wait to start with Williams Racing," Vowles said. "It's an honour to join a team with such an incredibly rich heritage.
"The team is an icon of our sport, one I greatly respect, and I am very much looking forward to the challenge.
"Mercedes have been hugely supportive on my journey, and we part on excellent terms after over 20 years of working in Brackley. I am grateful for everything Toto [Wolff] and the team have provided, and it has been such a special experience to journey together through failure and success.
"Williams Racing have placed their faith and trust in me, and I will do the same in return. Williams has tremendous potential, and our journey together starts in a matter of weeks."
The Williams F1 team, which won nine constructors' championships in the 1980s and 1990s, finished last in four of the last five F1 championships following a steady decline in recent decades.
Vowles' predecessor Capito was employed by current owners Dorilton Capital to turn the team around after the investment company bought it from the Williams family in August 2020. He lasted two seasons, overseeing initial progress in 2021 with an eighth-place finish in the championship, before Williams slumped to last place under new technical regulations last year.
Technical director Francois Xavier Demaison, who Capito recruited to Williams after working with him at Volkswagen, also left in December last year.
Matthew Savage, chairman of owners Dorilton, said: "We are delighted to welcome James to Williams Racing. He is one of the most highly respected talents in Formula One and will bring performance.
"He has been a key part of some of the most impressive feats in the sport over the past 15 years. As we continue our relentless pursuit for results, we believe that the appointment of James reinforces our dedication to ensuring we have energetic, experienced, and strong leadership as we move into the next phase of transforming Williams Racing."
Williams is due to host a preseason launch event at its factory on Feb. 6 at which drivers Alex Albon and new American signing Logan Sargeant will unveil the team's new car livery for 2023.