Williams appoint Mercedes strategy chief as new F1 team boss
Vowles replaces Jost Capito, who stepped down from his position as Williams CEO and team principal in December after two years in charge of the Grove-based outfit.
The 43-year-old will officially start work at Williams on February 20 after leaving Mercedes after leading the eight-time constructors' world champions strategy for more than four years.
Vowles previously held engineering and strategy roles at BAR, Honda, and Brawn GP, where he played a crucial role in overseeing race strategy during Jenson Button's title-winning campaign in 2009.
"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.”
Mercedes thanked Vowles for his "enormous contribution" to the team.
"James has been a highly valued member of our team in his role as Motorsport Strategy Director, playing an integral part in our success in recent years," said Mercedes boss Toto Wolff.
"Having worked with him since I first joined the team in 2013, I know how diligent, capable and talented he is and have taken great satisfaction from watching James develop and grow over the past decade.
"Since stepping back from the pit wall mid-season last year, he has continued to build the capability of our strategy team at Brackley, and we have a fantastic group of talented strategists who will continue their superb work in the years to come.
"While we are naturally sad to be saying goodbye to such a capable member of the team, I have no doubts whatsoever that he has all the necessary skills to become a fantastic Team Principal in Formula One.
"We wish him every success and are delighted that he will take this next step in his career with Williams, a strong technical partner of ours and one that has a place close to my own heart.”