The 1984 FIA Formula One World Championship was the 38th season of FIA Formula One motor racing. Drivers and teams competed in sixteen Grands Prix for the World Drivers' and World Constructors' championship titles. The season ran from 5 March to 21 October.

In the Drivers' Championship, the season became a duel between McLaren drivers Alain Prost and Niki Lauda. Prost won seven races to Lauda's five, including the last two races of the season, but Lauda eventually prevailed by half a point – the smallest margin in Formula One history. It was Lauda's third title and his first since 1977. McLaren comfortably won the Manufacturers' Championship, their first since 1974.

The season had been expected to see a continuation of the Brabham–Renault–Ferrari battle from 1983, with supporting roles for McLaren, Williams and Lotus. McLaren however had stolen a march on its competitors thanks to its TAG turbo engine and the John Barnard-designed MP4/2. The combination of dual World Champion Lauda, nine time Grand Prix winner Prost, the TAG-Porsche and the MP4/2 quickly became the class of the field.

FISA had introduced new fuel economy rules aimed at reducing speeds, ruling that cars powered by turbocharged engines would only have 220 liters of fuel per race, with re-fueling now banned (the tank had to be 220L, but teams were free to try and squeeze more in if they could, which some tried with methods such as freezing the fuel inside the tank). TAG, while still a sponsor with Williams, became a partner with McLaren team boss Ron Dennis, and commissioned German sports car manufacturer Porsche to design and build what would become the TAG-Porsche V6 turbocharged engine. Porsche had extensive experience with similar economy rules due to its participation in endurance racing (which included the 24 Hours of Le Mans) and this translated in superior fuel economy. Coupled with the superior aerodynamics of Barnard's MP4/2 (especially at high speed), this made the McLarens almost unbeatable in races throughout the season.

Reigning World Drivers' Champion Nelson Piquet and his Brabham-BMW were usually the fastest combination on track, which resulted in the Brazilian taking 9 pole positions. However, appalling early season reliability saw the reigning World Drivers' Champion failing to score a point in the first six rounds due to numerous engine and turbo failures, which meant he was never able to challenge consistently. Despite his back-to-back wins in Canada and Detroit, by halfway through the season it was apparent Piquet would not be able to defend his title, though he continued to fight hard until the end of the season, leading several races before either retiring or being forced to slow when running low on fuel.

The season saw a titanic battle between both McLaren drivers Niki Lauda and Alain Prost. Prost had been sacked by Renault two days after the 1983 season ended for openly criticising the team for failing to develop the RE40 during the season, resulting in the loss of both the Drivers' and Constructors' championships. Fast and ambitious, the Frenchman quickly established his dominance over his teammate, especially in qualifying, though Lauda's race driving saw him often a match for his younger teammate.

Austrian Niki Lauda, the 1975 and 1977 World Champion when driving for Ferrari, had returned to F1 in 1982 after his early retirement towards the end of 1979 and soon showed he had lost nothing of his earlier determination and guile. He regularly matched the pace of his 1982–1983 McLaren teammate John Watson, but Alain Prost (himself never the absolute fastest in F1) was a different kettle of fish. Lauda quickly realized he could not beat his young teammate on speed, therefore the wily Austrian often ignored qualifying and concentrated on his race strategies. By winning races when Prost ran into trouble and scoring relentlessly when Prost proved quicker, Lauda was able to win the title by just half a point. He also became only the second driver after New Zealand's Denny Hulme in 1967 to have ever won the title without achieving a single pole position in the season.

Prost though can be considered unlucky not to have won his first World Championship. He won 7 races to Lauda's 5, and lost a potential 4.5 points when the Monaco Grand Prix was stopped early. During the race, Prost had signalled on laps 29 and 31 that the red-flag should be shown, due to the ostensibly dangerous wet-weather conditions. Clerk of Course Jacky Ickx stopped the race after 31 laps, which he also explained was due to the dangerous conditions brought on by constant rain. Prost won the race from the Toleman of Ayrton Senna and the Tyrrell of Stefan Bellof, but only half points were awarded as the race was stopped before half-distance. The decision to stop the race was controversial as Ickx had not consulted with the race stewards before showing the red flag, an action which saw his suspension from being the Clerk of the Course. It was rumoured that Ickx, who at the time the lead driver in the factory backed Rothmans Porsche Sportscar team, had stopped the race when he did so that the Porsche engined McLaren would win and not the Hart engined Toleman of F1 rookie Senna. At the time Senna had been showing what would become legendary wet weather driving skills and was catching the more experienced Prost very quickly. Senna actually passed the slowing Prost as they crossed the line when Ickx held out the red flag (Prost had slowed down having already been told on the team radio that the race had been stopped), but the regulations ruled that the results were taken from the previous lap, where Prost still held a 7.4 second lead. Almost going unnoticed in Senna's late race charge for the lead, was that the Cosworth V8 powered Tyrrell of Bellof (a teammate of Ickx's in the Rothmans Porsche sportscar team) was catching Senna as fast as the Brazilian was catching Prost. Toleman mechanics later confirmed that had the race not been stopped, Senna would not have finished as the TG184 had suffered serious suspension damage due to his constant running over the high curbs at the Nouvelle Chicane.

During the season, the Tyrrell team had its results stripped after a technical infringement. Soon after the podium ceremony for the Detroit Grand Prix in which Martin Brundle had finished in second place (only 2 seconds behind the Brabham of Nelson Piquet), word arrived that the officials had found impurities in the water injection system on his Tyrrell 012 and lead balls in the rubber bag containing the water. Samples of the water were shipped to France and Texas for analysis and found to contain significant levels of hydrocarbons. Team boss Ken Tyrrell was called to a meeting of the FISA Executive Committee on July 18 and, based on the impurities in the water, which had been topped up during a pit stop, was accused of refueling the car during the race. Refueling had been banned prior to the 1984 season and remained illegal until 1994. FISA found the team guilty and Tyrrell was disqualified from the remainder of the World Championship and lost the 13 points they had already gained as of Detroit. They were allowed to and did continue to race, though they did not appear for the final three races of the season. However, they were unable to score any championship points. Many in the paddock felt for Tyrrell as they believed the penalty far outweighed the crime and that FISA boss Jean-Marie Balestre had used the system to make an example of the British-based team to vindicate what happened the previous season, when Brabham escaped punishment after admitting to run a lighter car by using a different blend of fuel.

McLaren dominated the season, with Prost winning 7 races to equal the season wins record set by Jim Clark in 1963, and Lauda winning 5, making the McLaren MP4/2 the most dominant single season car in the sports history to that point. The team also scored four 1–2 results during the season to easily win the Constructors' Championship with a then-record 143.5 points, some 86 points in front of second-placed Ferrari. McLaren won 12 of the season's 16 races, with Brabham's reigning World Champion Nelson Piquet scoring two wins. Michele Alboreto (Ferrari) and Keke Rosberg (Williams-Honda) were the only other winners in the season with each winning a single race.

For Japanese giant Honda, Rosberg's win in the Dallas Grand Prix in the United States would be the first of 40 wins for their turbocharged V6 engines until the turbos were banned following the 1988 season. It was also Honda's first win in Formula One since John Surtees had won the 1967 Italian Grand Prix at Monza driving the V12 powered Honda RA300 in its debut race. The Dallas Grand Prix was a one-off race, as the race was inexplicably run during the 100F heat of a Texas July summer; the weather and track temperatures were so high that the track broke up very badly. Aside from those problems, the circuit and the organization were well-received, and race was a classic- but only 7 cars finished. This was similar to the previous race in Detroit, where only 6 cars finished. Renowned British motorsports journalist Denis Jenkinson referred to these 2 American races as "demolition derbies".