The Williams FW11 is 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 1,200 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.