The Ligier JS9 was a racecar designed by Gérard Ducarouge and Michel Beaujon. The car raced during the 1978 season of Formula One.

The car made its debut at the 1978 Spanish Grand Prix being driven by Jacques Laffite (who drove the car throughout the season. The car started in 10th on the grid and managed to finish 3rd overall.

The JS9 was fitted with a Matra MS78 V12 engine and rode on Goodyear tyres. The JS9 had a chassis of an aluminium monocoque design. The car weighed 580kg, had a 210l capacity fuel tanks and was fitted with a Hewland FGA 400 gearbox.

Under Jacques Laffite, the JS9 had a successful racing career, finishing in the top 10 in 9 of her races. She was retired from the 1978 Canadian Grand Prix for transmission problems and never raced again.