IMSA — the International Motor Sports Association — sanctions North America's premier sportscar series, the IMSA SportsCar Championship (officially the WeatherTech SportsCar Championship under its title sponsor). Its defining feature is multi-class racing: several types of car share the same track at once, each fighting for its own class title.
Four classes compete together:
- GTP (Grand Touring Prototype) — the fastest, headline class of purpose-built hybrid prototypes, built to rules shared with world endurance racing.
- LMP2 (Le Mans Prototype 2) — spec prototypes a clear step below GTP, popular with independent teams.
- GTD Pro (GT Daytona Pro) — production-based GT3 cars run by all-professional driver lineups.
- GTD (GT Daytona) — the same GT3 machinery, but with pro-am crews that include an amateur-rated driver.
Because a sportscar race can last for hours, each car is shared by a multi-driver crew who swap over during pit stops. The calendar mixes short sprints with endurance classics — most famously the Rolex 24 At Daytona and the 12 Hours of Sebring — and the longest races also feed a separate Michelin Endurance Cup. New to it? See how an IMSA race weekend works.