Currently The United States's premier series for sports car endurance racing, formed in 2014 from the merger of two rival sanctioning bodies - the Rolex Sports Car Series and the American Le Mans Series.
- Rolex was founded in 1999 under the auspices of the Grand-Am Road Racing Association, which was run by members of the NASCAR community and was eventually purchased outright by NASCAR Holdings in 2008 in an effort to more efficiently run both racing bodies. Even without this, it was always heavily tied to NASCAR due to the use of a special road course setup at Daytona International Speedway, which has hosted the 24 Hours of Daytona since 1966 (The first 2 runnings in 1962-63 were 3 hours, and the next two 2000 miles). The organization originally bore some resemblance to the various Le Mans series run worldwide, initially using SR Ps(Sports Racing Prototypes, a general term and division for Le Mans Prototypes), the GTS and GT classes among others, but diverged significantly starting with the introduction of its own unique prototypes in 2003(known as Daytona Prototypes).
- American Le Mans Series (ALMS) was also started in 1999 by Don Panoz, in partnership with Automobile Club de L'Ouest, the sanctioning body for the 24 Hours of Le Mans, which allowed it to use the exact same cars and classes as used in that race, although some classes were dropped or modified at various points in the series' existence.
The two organizations announced the merger in late 2012, and revealed the class structure for the new series in March 2013 at Sebring.
The classes for the 2019 and 2020 seasons are as follows:
- Daytona Prototype International (D Pi) - The top class in the series. Cars used here are Modified LM P2s (see below) that have custom bodywork and engines, both of which are manufacturer-associated.
- Le Mans Prototype 2 (LMP 2) - Prototypes that adhere to the ACO LMP 2 regulations, with a spec Gibson V8 engine and any one of 4 chassis.
- GT Le Mans (GTLM) - This class is nearly the same as the GTE Pro class from the World Endurance Championship, with the same cars(which are race versions of supercars and grand tourers found on the road) and different, independent Balance of Performance regulations.
- GT Daytona (GTD) - A former merger class, which combined the GT and GXnote classes from Rolex with the GT Challenge class from ALMS. It was gradually consolidated into only consisting of FIA-homologated GT 3 cars.
The series was sponsored by Tudor, a "discount" watch brand owned by Rolex, which has sponsored the 24 Hours of Daytona since 1991. Current sponsorship comes from car floor mat manufacturer Weather Tech. The schedule consists of various events carried over from both the previous series, including Daytona, The 12 Hours of Sebring, the 6 Hours of Watkins Glen (carried over from Rolex) and the 10 hour Petit Le Mans at Road Atlanta (carried over from ALMS),note which together comprise a sub-championship called the Michelin Pilot North American Endurance Cup (MPNAEC). While all classes are run together at the endurance races, most of the sprint races will exclude a class.