1989 Formula One World Championship

The 1989 FIA Formula One World Championship was the 43rd season of FIA Formula One motor racing. It began on 26 March and ended on 5 November. Alain Prost won his third Drivers' Championship, and McLaren won its second consecutive Constructors' Championship; its fifth overall.

The Drivers' Championship was decided in controversial circumstances at the penultimate race of the season in Japan, when Prost and teammate Ayrton Senna, who needed to win the race, collided in the closing laps. Prost retired while Senna rejoined the track after a push start and crossed the line first, only to be disqualified for not rejoining the track correctly. This handed Prost the title, his last with McLaren before joining Ferrari in 1990.

The season also saw an unprecedented number of entries, with 21 constructors originally entered, fielding a total of 40 cars. However, FIRST Racing withdrew from the championship before the opening race, leaving 20 constructors fielding a total of 39 cars, which remains the highest entry in the modern era.

This year was the first year of the new mandatory 3.5 litre engine formula following the FIA's ban on turbocharged engines following the conclusion of the previous season. Renault also returned as engine supplier for the first time since 1986 with both Renault and Honda developing engines with a V10 configuration, an engine configuration never previously used in Formula One.

As of 2025^[update], this was the last time Honda and the same engine manufacturer won both the Formula One and MotoGP world manufacturers' titles in the same year.

The following teams and drivers competed in the 1989 FIA Formula One World Championship. FIRST Racing injected material into their chassis in order to pass a mandatory FIA pre-season crash test, however, it made its car significantly overweight and they withdrew before the opening Brazilian Grand Prix. After this, they instead focused on the Formula 3000 series. Changes to the technical regulations, including the outlawing of forced-induction engines, contributed to the bumper entry.

McLaren, having won fifteen of the sixteen races in 1988, kept their successful driver line-up of 1985 and 1986 World Champion Alain Prost and defending champion Ayrton Senna. They would drive the new MP4/5 powered by a Honda V10 engine.

Ferrari completed the signing of British driver Nigel Mansell, taking the place of Michele Alboreto alongside Austrian Gerhard Berger. The new 640, designed by John Barnard, featured a semi-automatic electronic gearbox, the first of its kind, as well as the team's first 12-cylinder engine since 1980.