Williams has confirmed Paddy Lowe, who has been on a leave of absence since March 5, has now left the team and stepped down from the board of directors.
Lowe's leave of absence was confirmed on the eve of the current season, after the team missed the start of F1 pre-season testing and endured a difficult winter. It has been rooted to the foot of the pecking order at every race this year.
On Tuesday, it was confirmed Lowe, who joined from Mercedes in 2017, has left with immediate effect.
"After a period of careful reflection I have reached the decision that I will not return to work at Williams," Lowe said in a statement. "I wish all my previous colleagues the very best to meet the challenges ahead, which I am sure they will do. I would especially like to thank the Williams fans who are so supportive."
Deputy team boss Claire Williams said: "We understand and respect the decision Paddy has reached and wish him well for the future."