The following teams and drivers participated in the 2018 FIA Formula One World Championship. All teams competed with tyres supplied by Pirelli.
McLaren terminated their engine partnership with Honda and instead signed a three-year deal for power units supplied by Renault. The team cited Honda's repeated failure to supply a reliable and competitive power unit as the reason for ending the partnership.
Toro Rosso parted ways with Renault – allowing McLaren to finalise their agreement with Renault – and came to an agreement to use Honda power units. As part of the deal, Red Bull Racing loaned Toro Rosso driver Carlos Sainz Jr. to Renault's works team.
Sauber renewed their partnership with Ferrari, upgrading to current-specification power units after using year-old power units in 2017 and also signed a sponsorship deal that saw Alfa Romeo become their title sponsor.
Force India were placed into administration on 27 July 2018, during the Hungarian Grand Prix weekend. After speculation of a purchase, any sale of the team in a short time-span was complicated by legal proceedings against certain shareholders and the need for debt settlement. A consortium led by Lawrence Stroll purchased the racing assets and operations of Force India through a company named Racing Point UK Ltd. The original team, known as "Sahara Force India", was then excluded from the Constructors' Championship on the grounds of their inability to participate in remaining races. This allowed a new team known as "Racing Point Force India" to apply for a late entry and start their participation in the championship from the Belgian Grand Prix. The team was required to keep "Force India" as part of their constructor name as their chassis had been homologated under the Force India name and Formula One sporting regulations required the constructor name to include the chassis name. The new team began with zero points in the Constructors' Championship, though their drivers retained the points they had scored in the Drivers' Championship. The other teams later agreed to allow the Racing Point Force India team to retain prize money accrued by Sahara Force India in the preceding years.
Toro Rosso signed 2016 GP2 Series champion Pierre Gasly and two-time World Endurance champion Brendon Hartley as their full-time drivers for 2018. Both Gasly and Hartley made their Formula One débuts with the team in the latter stages of the 2017 championship. Daniil Kvyat left the team and the Red Bull driver programme, securing a development role with Ferrari.
Charles Leclerc, the reigning Formula 2 champion, made his competitive début with Sauber. Leclerc, who had previously driven in Friday practice sessions in 2016 and 2017, was hired by the team to replace Pascal Wehrlein. Wehrlein was ultimately unable to secure a race seat and was instead enlisted as one of Mercedes's test and reserve drivers while racing full-time in the Deutsche Tourenwagen Masters series.
Williams driver Felipe Massa retired from Formula One at the end of the 2017 championship. Massa was replaced by former Renault test driver and SMP Racing driver Sergey Sirotkin, who made his competitive début with the team.