The first use of what would become Le Mans Prototypes occurred at the 1992 24 Hours of Le Mans, with older Porsche 962s allowed entry in Category 3 and small open-cockpit race cars using production road car engines permitted in Category 4. Later, the Automobile Club de l'Ouest (ACO) announced its intention to replace Group C cars with Le Mans Prototypes, creating two classes: LMP1 and LMP2. LMP2 cars originally used smaller displacement, production-based engines, with both classes requiring open cockpits.
In 1998, the ACO greatly altered these classes. The smaller LMP2 class was briefly eliminated, while a new class of closed-cockpit prototypes known as "LMGTP" (Le Mans grand touring prototype) was introduced for advanced cars that the ACO considered too fast for GT regulations.
In 1997, the first European series based around Le Mans Prototypes was launched, known as the "International Sports Racing Series," with classes similar to LMP1/WSC and LMP2 referred to as "SR1" and "SR2" by the FIA. The 1998 season saw further expansion with the creation of the American Le Mans Series, which used the same class structure as the 24 Hours of Le Mans and was the first championship to officially use the LMP name.
From 2017, the FIA introduced a new set of LMP2 regulations to limit costs. These regulations aimed for a significant power decrease in the range of 150 horsepower, which was expected to lead to a four-second decrease in lap time at Le Mans. Gibson Technology became the exclusive engine supplier for the class, producing a 4.2-litre naturally-aspirated V8.
From 2017 through 2020, the Gibson engine produced around 600 bhp. Dallara, Onroak Automotive (Ligier), Oreca, and the joint-venture Riley Tech/Multimatic were selected by the FIA as the four exclusive chassis constructors, which must be closed-cockpit designs.
Before the 2021 season, LMP2 cars were slowed to ensure a lap time difference between LMP2 and the new Le Mans Hypercar class. The power of the Gibson engine was initially reduced to 560 bhp, then further weakened to 540 bhp. The minimum weight was increased by 20 kg to a total of 950 kg. Additionally, a single aero kit was mandated for the season, limited to the Le Mans specification in the WEC, though ELMS teams retained the right to switch between kits. Oreca and Ligier have been selected as constructors for the 2028 regulations, with Gibson continuing as the engine supplier.
LMP3 is an entry-level prototype class intended for introducing young drivers and new teams to endurance racing. It uses closed-cockpit chassis with capped costs for the chassis and engines.
Cars eligible for the 2015–2019 first-generation ruleset included the Ginetta-Juno P3, Ligier JS P3, Norma M30, ADESS-03, and the Ave-Riley AR-2. A second generation was introduced for 2020, featuring the Ginetta G61-LT-P3, Ligier JS P320, Duqueine D-08, and the ADESS-03 Evo. From 2025, a third generation will utilize a twin-turbocharged 3.5-litre Toyota V35A engine producing 350 kW (470 hp), with the weight limit increased to 1,000 kilograms (2,205 lb).
Prior to the current ladder, the Le Mans Prototype Challenge (LMPC) served as an entry-level class starting in 2009. This class consisted of competitors running identical Oreca FLM09 cars. LMPC was dropped from the European Le Mans Series in 2014 and from the WeatherTech SportsCar Championship after the 2017 season, as the costs of running the team were found to be comparable to those of the LMP2 class.