The Ligier JS21 was a racecar which was designed by Michel Beaujon and Claude Gallopin. The cars were raced during the 1983 Season of Formula One.

The cars made their debut at the 1983 Brazilian Grand Prix, with two cars being entered. The first car was driven by Jean-Pierre Jarier, the second by Raul Boesel. Both of the drivers failed to finish the race due to mechanical problems.

The cars were fitted with a Ford Cosworth DFV V8 engine and they rode on Michelin tyres. The cars had a chassis of an aluminium monocoque design. The cars weighed 540 kg, they had a 210L fuel tank and they were fitted with a Hewland FGB gearbox.

The cars were not very successful with a number of mechanical problems halting their efforts to gain points for the team.