The twin-engined Gulfstream-IV came down at Castellet airport, between Marseille and Toulon, with all the victims believed to have died on impact.
They were described by an airport source as two men aged 24 and 61, and a woman aged 30. Nobody else was on board.
The jet, which was flying in from nearby Nice, split in two, with one half ending up in a nearby lake after narrowly missing a hotel.
Fire engines were called to the scene as the main cabin blazed on the runway, but nothing could be done to save those on board, said the same source.
“It was an appalling accident – an investigation has already started,” said the source, who said the accident happened at around 3:00 p.m.
He added: “All the victims are American passport holders.”
Castellet International Airport was built by the late French pastis tycoon Paul Ricard in 1962.
It is the largest private airfield on the French Riviera, and frequently used by celebrities with homes in the area, as well as business people.
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