The McLaren MP4/6 is a Formula One racecar that was designed by Neil Oatley for the 1991 F1 season. It was the first McLaren to be powered by a Honda V12 engine. The car was tested by Gerhard Berger in the off-season, but he was unimpressed with the new engine, feeling it was underpowered for what it was, especially compared to Honda's V10 engine in the previous year's car. When Ayrton Senna returned for pre-season testing, he knuckled down to try to solve the engine's problems. McLaren's domination in the early part of the year was mainly due to the lack of reliability of the Williams FW14.

The MP4/6 raced throughout 1991 with a manual H pattern gearbox. A semi-automatic transmission was tested during the season, but was never regarded as good enough to be used in a race. Ferrari and Williams were the only teams using semi-automatic gearboxes during 1991. This makes the MP4/6 the last Formula One car to win a World Championship, either drivers or constructors, using a manual transmission or a V12 engine.

Senna won the first four races of the season, in the United States, an emotional victory in Brazil, San Marino and Monaco before...