The Matra MS84 was the fifth Formula One car produced by Matra (following the MS9, MS10, MS11 and MS80). The Ford Cosworth DFV-powered car (engine 3000 cc, estimated at around 420 bhp (313 kW))

The car was built at Matra's Formula One base at Vélizy-Villacoublay in the southwestern suburbs of Paris, designed under the direction of Bernard Boyer and built by Jean Bee (a.k.a. "Bunny") under the direction of Legan. It was run by the Matra International team of Ken Tyrrell with full technical support from Matra and the financial backing of Elf.

Although it has a family resemblance with the MS80 with which Matra won the 1969 Constructors' Championship, it is a completely different car with a steel tube chassis instead of an aluminium monocoque. At the back the engine is mounted back-to-front with the gearbox directly behind the driver. The four wheel drive suspension is similar in design to the one that was installed on Tony Rolt Ford Mustangs. Ferguson transmission and other necessary additions left the car much heavier than the two-wheel drive sister cars (635 kg with no fuel). Like the Lotus 63, the MS84 made its first appearance at the Dutch Grand Prix, where Jackie Stewart tried the car out but opted to use his MS80, as he would for the rest of the season.

The car was still present at all the remaining races as a spare, and at Silverstone Jean-Pierre Beltoise gave the car its first race and came home ninth, six laps behind Stewart's two-wheel drive Matra (but three laps ahead of John Miles's Lotus 63). By the next time the car raced, the front differential had been disconnected and the car effectively ran as an over-weight MS80 with inboard front brakes, memorably giving the lie to Johnny Servoz-Gavin's protestations about the 4WD car being "undriveable" after he finished the Canadian Grand Prix six laps down in sixth place. Servoz-Gavin also drove the car at Watkins Glen, finishing 16 laps down and unclassified, and finally in Mexico, crossing the line "just" two laps down in eighth place. Although there was a project for a 4WD Matra MS 124, the MS84 was never replaced.

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