The McLaren MP4/1 (initially known as the MP4) was used during the 1981, 1982 and 1983 seasons. It was the second Formula One car to use a monocoque chassis wholly manufactured from carbon fibre composite, after the Lotus 88 (which never raced), a concept which is now ubiquitous. The MP4/1 was first entered in a Formula One race at the third grand prix of the season in Argentina.

The chassis was designed by John Barnard, Steve Nichols and Alan Jenkins, with the car being powered by a Cosworth DFV engine.

The MP4 was the first car to be built following the merger of the McLaren team and Ron Dennis' Project 4 Formula 2 team; its designation was short for "Marlboro Project 4".

The main engineer for the MP4 was John Barnard, who began drawing the car in late 1979. After a visit to the Rolls-Royce factory where he saw engineers working with carbon fibre technology on the Rolls-Royce RB211 jet engine, Barnard saw the potential of this technology and convinced Ron Dennis to fund the design and build of a whole new car out of this new bodywork material. The chassis itself was built by McLaren using carbon supplied by American firm Hercules Aerospace in Salt Lake City on the advice of McLaren engineer and former Hercules apprentice Steve Nichols, and quickly revolutionised car design in Formula One with new levels of rigidity and driver protection and its Carbon-Fibre-Composite (CFC) construction. Dennis and Barnard took Nichols' advice after being rejected by multiple British firms due to the ambitiousness of this method of chassis construction. Within months and subsequent years carbon fibre started being used by all of McLaren's rivals. The car was far more advanced than any of McLaren's previous cars- including its predecessor, the M29 and M30, and its design and construction was of a far more precise nature than before- just about at the level of fighter aircraft.

From 1981 until late 1983 the MP4/1 was powered by the 3.0 litre Ford-Cosworth DFV V8 engine, but in late 1983 the team switched to turbocharging, using a 1.5 litre TAG V6 engine built by Porsche.

In both 1981 and 1982 McLaren International benefited from the exclusive use of a development Nicholson-McLaren Cosworth DFV which powered the MP4. Developed and re-built in John Nicholson's Colnbrook workshops (an agreement with McLaren going back to the mid-1970s) the Nicholson DFV featured bigger pistons and valves that a conventional factory DFV, and thus could rev to around 11,500 RPM, producing around 510 BHP, enabling John Watson and Niki Lauda to all but match the factory Ferrari and Renault V6 twin-turbos in straight line speed during the 1982 season. The Nicholson DFV also used different castings to reduce frictional losses, as well as using MAHLE pistons rather than Cosworth's in house piston/con rods.

Hercules Aerospace keeps John Watson's car which was destroyed in the 1981 Italian Grand Prix and shows it off to visitors after allowing them to view footage of the accident, highlighting how it was possible for him to survive in a carbon fibre car.