Niels Wittich has left his role as Formula 1's race director with immediate effect.
The German, who had been in the role since 2022, "has stepped down from his position to pursue new opportunities," the FIA said in a statement to BBC Sport.
He will be replaced from the next race in Las Vegas by Rui Marques, most recently the race director for Formula 2 and 3.
The surprise move has happened quickly. FIA staff were told earlier on Tuesday, BBC Sport has been told.