Super Taikyu began in 1991 as the N1 Endurance Series, built around production-car categories derived from the FIA Group N regulations. For its first two decades the series fielded only its domestic displacement-based classes. In 2011 the series expanded by admitting SRO-homologated GT3 cars, initially under the name ST-GT3, which was later relabelled ST-X. The decision reflected a broader globalisation of GT3 racing; by the early 2010s GT3 regulations had become the dominant framework for gentlemen driver endurance and sprint series worldwide, and incorporating ST-X allowed Super Taikyu to offer international-specification machinery alongside its traditional Japanese domestic classes.
Two further international categories have since been added: ST-Z for SRO GT4 machinery, introduced in 2017, and ST-TCR for touring cars conforming to the globally used TCR regulations, also introduced that year. An additional category, ST-Q, arrived in 2021 for manufacturer-developed experimental vehicles operating outside standard homologation, followed by ST-USA in 2025 for IMSA-used American GT cars.
ST-X cars must hold current SRO GT3 homologation. This requirement ties the class directly to the international homologation calendar and ensures that the vehicles competing in Japan are the same machinery used in GT World Challenge Europe, the Intercontinental GT Challenge, and other major international GT3 series. Balance of Performance is applied to level the field across manufacturers.
Super Taikyu is run on a pro-am basis, and ST-X reflects this ethos: grids typically combine professional racing drivers with amateur gentlemen competitors sharing the same car over endurance race distances. Formats vary by round, ranging from five-hour races to the Fuji Super TEC 24 Hours at Fuji Speedway, which has been the series' flagship event since its revival in 2018. The previous benchmark was the Tokachi 24 Hours, held annually from 1994 to 2008. ST-X cars, with their superior power and aerodynamic downforce, are the fastest in the field and set the overall pace at these events.
The ST-X class has attracted factory-affiliated programmes from most of the leading GT3 manufacturers operating in Japan. Japanese brands including Toyota, Nissan, Honda, and Subaru have all featured, alongside European manufacturers whose GT3 cars are represented through importer-backed or private teams. The class serves as a showcase for the latest GT3 homologation cycles and benefits from the ongoing development that manufacturers invest in globally competitive GT3 programmes.
The introduction of the ST-X class marked a turning point in Super Taikyu's competitive profile, elevating the series from a purely domestic production-car championship to a venue for internationally recognised GT3 machinery. It has strengthened the series' prestige, helped attract larger manufacturer and sponsor involvement, and given Japanese drivers a competitive platform at home that is directly comparable to major overseas GT3 series. The class runs concurrently with the domestic ST-1 through ST-5 classes, preserving the series' original production-car identity while offering an international benchmark at the front of the grid.