The 1986 Portuguese Grand Prix was a Formula One motor race held at Estoril on 21 September 1986. It was the fourteenth race of the 1986 FIA Formula One World Championship.

The race was won by British driver Nigel Mansell, driving a Williams-Honda. Brazilian Ayrton Senna took pole position in his Lotus-Renault, but Mansell passed him at the start and led the entire race, also setting the fastest race lap. Senna held on to second place until he ran out of fuel on the final lap and dropped to fourth, promoting Frenchman Alain Prost in the McLaren-TAG to second and Mansell's Brazilian teammate Nelson Piquet to third.