The Williams FW11 was a Formula One car designed by Frank Dernie as a serious challenger to McLaren and their MP4/2C car. The car took over from where the FW10 left off at the end of 1985, when that car won the last three races of the season.

The FW11's most notable feature was the Honda 1.5 litre V6 turbo engine, one of the most powerful in F1 at the time producing 800 bhp at 12,.000rpm and well over 1200 bhp at 12.000 rpm in qualifying.

Added to the engine's power were the aerodynamics, which were ahead of the MP4/2C and the Lotus 98T. That and its driving pairing of Nelson Piquet and Nigel Mansell made it a force to be reckoned with.

In 1986, the car won first time out in Brazil with Piquet.

The FW11 was updated slightly for 1987 to become the FW11B, and the team made no mistakes in wrapping up both championships.

The FW11 was not a technical showcase by any means, but solid engineering, exceptional aerodynamics, the engine's outright power and superior fuel economy (even better than the TAG-Porsche engines used by McLaren), and Piquet and Mansell helped the car take 18 wins, 16 pole positions and 278 points over two seasons of racing.

An interim car that was tested before the FW11's successor FW12 was finished, the FW11C was used for the Judd V8 engine powering the FW12 in 1988. It was only built for testing purposes and it never raced.