Mid-Ohio Sports Car Course is a road course auto racing facility located in Troy Township, Morrow County, Ohio, United States, just outside the village of Lexington. It hosts a number of racing series such as IndyCar, IMSA WeatherTech Sportscar Championship, and the NASCAR Craftsman Truck Series, along with other club events such has SCCA and National Auto Sport Association.

There is grandstand seating for 12,000 spectators and three observation mounds alongside the track raise the capacity to over 75,000. Mid-Ohio is classified as an FIA Grade Two circuit.

The track opened in 1962 as a 16-turn road course run clockwise. After only one year, the "Oak Tree Bend" series of turns (in the northeast corner) was removed due to being too slow. It was replaced by the "Thunder Valley" downhill straight, which remains to the present day. For 1963 and beyond, a 15-turn, 2.400 mi (3.862 km) layout was established. The back portion of the track allows speeds approaching 200 mph (320 km/h). A separate starting line and flagstand is situated on the backstretch to allow for safer and more competitive rolling starts. The regular start/finish line is located on the pit straight.

In 1990 the track underwent a refurbishment. A new retaining wall was built, the entire track was resurfaced, widened and concrete was paved in the apexes of the turns to prevent asphalt deterioration. In addition, a straightaway segment was paved through the chicane, allowing for two different track layouts, the original 2.400 mi (3.862 km) circuit and a new 13-turn, 2.258 mi (3.634 km) circuit which bypasses the chicane. Major series including CART/Champ Car, IndyCar, IMSA, and NASCAR have mostly elected to bypass the chicane, while motorcycles and amateur/club racing typically use the 2.4-mile layout (with the chicane).

In 2006 another major refurbishment saw several improvements. The entire circuit was repaved and the concrete patches in the turn apexes were removed. A new motorcycle "short course" was created by connecting turn one with the backstretch and another motorcycle/autocross oval was created by connecting the chicane straight with the backstretch. The additional layouts allow simultaneous use of the multiple courses, for instructional and competitive uses. The improvements also included a motocross facility, that has since been used for the AMA Vintage Motorcycle days event.

In 2019 the ARX came to the track which was the first time rallycross had come to the circuit. The course was a 10-turn, 0.7 mi (1.1 km) and utilized the keyhole section of the track.

At the conclusion of the 2023 season, the track was once again fully repaved after utilizing a test section in turn one.

In the fall of 2024, Turn 4 was refurbished. Its original 4-degree banking was reduced to 2 degrees, its runoff area, known as “China Beach,” was regraded to the same level as the track. Additionally, new access roads were added near the runoff to better accommodate maintenance and safety vehicles. Catch basins were installed in the turn to facilitate drainage.