Mark Gillan, one of the architects of Williams's 2012 revival, has left the team.
Gillan had joined Williams during its troubled 2011 Formula 1 campaign and was appointed as its chief operations engineer during its technical reshuffle.
The team confirmed to AUTOSPORT that Gillan had vacated his role to "spend more time with his family".
Williams declined to comment on any plans to replace Gillan.
The squad endured its worst F1 season since the 1970s in 2011, finishing a distant ninth in the constructors' championship.
But this year Williams recovered its form and while its position in the standings only improved by one place, it was a regular frontrunner again and won the Spanish Grand Prix.
Pastor Maldonado's Barcelona win was Williams's first since the 2004 Brazilian GP.
Prior to joining Williams, Gillan had held positions at McLaren, Jaguar/Red Bull and Toyota, where he was head of aerodynamics in the team's final F1 seasons.
Edd Straw, F1 editor
Mark Gillan played a key role in the Williams revival after joining at the start of October last year, at a time when the team was in the midst of a dismal season.
Gillan, who had previously worked for McLaren, Jaguar/Red Bull and Toyota Motorsport, brought a logical, methodical approach to running the race team that enabled it to unlock the potential of the machinery on a regular basis.
While Williams ultimately underperformed in the world championship, finishing eighth in the standings when it had the potential to finish fifth, it was a vast improvement on the 2011 campaign. The highlight was unquestionably Pastor Maldonado's sensational victory in the Spanish Grand Prix.
It is not yet clear what effect Gillan's departure will have on the team. Working under technical director Mike Coughlan, he was central to race weekend operations.
Who replaces him with could prove central to ensuring that Williams continues to build on the step forward it made in 2012.
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