The LMH class arose directly from the disintegration of the LMP1 Hybrid programme. Audi withdrew from the WEC at the end of the 2016 season and Porsche followed after 2017, both exits linked to the Volkswagen Group emissions scandal and to spiralling development costs in the hybrid sub-category. With the two manufacturers that had dominated endurance racing now absent, the ACO and FIA began exploring a successor framework capable of attracting a wider range of participants at a fraction of the previous expenditure. Initial discussions, which included IMSA as a potential co-regulator, targeted full-season budgets of approximately 25 million euros — roughly 75 percent below what manufacturer LMP1 teams had been spending. FIA President Jean Todt suggested renaming the category, and the ambition was for a unified rule set that could span the Daytona 24 Hours, Le Mans 24 Hours, and Sebring 12 Hours.
In June 2018, ahead of the 24 Hours of Le Mans, the FIA confirmed that the new class would be built around road-car-inspired hypercar design concepts. Toyota, Ford, McLaren, Aston Martin, and Ferrari were reported to have taken part in roundtable discussions with championship organisers. The initial technical framework envisaged a free engine architecture, a combined power target of up to 520 kW (700 hp) from the combustion unit and a 200 kW front-axle electric motor providing four-wheel drive, a minimum weight of 980 kg, and a target lap time at Le Mans of 3:20 — deliberately slower than LMP1 to constrain costs.
Scuderia Cameron Glickenhaus became the first manufacturer to declare participation on 25 July 2018, planning to fund its programme with a limited run of 25 road-legal versions. No other manufacturer committed before the year's end; McLaren formally withdrew from the inaugural season on 21 October 2018, citing tight timelines and the fluid state of regulations.
The FIA published the full technical rulebook on 5 December 2018. Production-based powertrains became mandatory, which excluded specialist racing constructors such as Oreca, Onroak Automotive, and Dallara. Manufacturers were required to produce at least 25 road cars incorporating the race car's combustion engine and energy recovery system (ERS) by the end of their first competitive season, rising to 100 by the end of the second. Diesel power was banned. The maximum combined power output was set at 785 hp (585 kW), with the electric MGU-K component capped at 200 kW; in practice, power units were governed by a prescribed combined power curve peaking at 585 kW at 95 percent of engine speed, not the headline sum of individual outputs. A 3 million euro cost cap was imposed on ERS supply, and any ERS manufacturer was restricted to supplying a maximum of three competitors without FIA approval. Minimum weight was raised to 1,040 kg, maximum length to 5,000 mm, and maximum cockpit width to 2,000 mm.
In March 2019 the FIA widened the rules to permit race cars derived from road-going hypercars, responding to manufacturer requests for closer alignment between production and racing activities. The target lap time was relaxed to 3:30 and movable aerodynamic devices were removed from the regulations. The full regulations were published at the 2019 Le Mans event, at which Toyota Gazoo Racing and Aston Martin Racing confirmed participation. Toyota indicated it would base its car on the GR Super Sport concept; Aston Martin confirmed use of the Valkyrie. In February 2020, Aston Martin postponed its hypercar project, citing the emerging LMDh regulations and its planned return to Formula One. In May 2020 the FIA approved a reduction in maximum power output to 500 kW (670 hp) and minimum weight to 1,030 kg.
In 2021, shortly after Peugeot unveiled its 9X8 hypercar, IMSA and the ACO announced the convergence of their top-level prototype rules into a single class. LMH and LMDh cars — the latter a lower-cost customer prototype specification — were permitted to race against each other in both the WEC Hypercar class and the IMSA GTP class. From 2023, LMH cars became eligible to compete in the IMSA SportsCar Championship alongside LMDh entries, establishing transatlantic competitive compatibility between Europe and North America at the top level of sportscar racing for the first time in several decades. In 2025, it was confirmed that Hypercar-class cars would be eligible to enter the Asian Le Mans Series with customer teams and Pro/Am driver lineups from the 2026/27 season.
LMH cars must present a frontal surface area of at least 1.6 m². Bodywork must conceal mechanical components when viewed from above, the sides, and the front, and movable aerodynamic elements are prohibited. Only four-stroke petrol engines are permitted; for production-derived units the block and head castings must originate from the road-car engine with only minor machining alterations allowed, the crankshaft may not be more than 10 percent lighter than standard, and camshaft quantities, angles, and locations must remain as in the original. For cars using an energy recovery hybrid system, the speed at which the front-axle MGU-K may apply positive torque is governed by a Balance of Performance table applicable to both slick and non-slick tyre conditions.