Stock car racing is a form of automobile racing found mainly in the United States held largely on banked concrete oval tracks of between approximately 1/2 mile and 2 miles (about 0.8 to 3.2 kilometres) in length, but also raced occasionally on conventional racing circuits. Ovals shorter than one mile (1.6 km) are called short tracks; longer ovals are typically known as superspeedways. Races are generally 200 to 600 miles (320-965 km) in length. Top speeds are around 160 mi/h (275.5 km/h), compared to 220 mi/h (354 km/h) in open wheel racing. (Some tracks are built to allow cars to travel at speeds close to those in open-wheel racing.)

Stock cars superficially resemble standard American family sedans, but are in fact purpose-built racing machines built to a strict set of regulations governing the car design ensuring that the chassis, suspension and such are architecturally identical on all vehicles. Ironically, these regulations ensure that stock car racers are in many ways technologically less sophisticated than standard cars on the road. For example, NASCAR (the premier stock car organization in the US) requires carbureted engines in all of its racing series, while fuel injection is now universal in standard passenger cars.

Engines, whilst containing varying components from the various manufacturers who compete in the series, are of fixed size, and are generally designed to ensure all entrants have near-equal vehicles. There are several categories of stock car racing, each with slightly different rules, but the key intention of cars that look like production cars, but with near-identical specifications underneath, remains true.

The most prominent championship in stock car racing is the NASCAR championship, currently called the Nextel Cup after its sponsor (formerly known as Winston Cup after a previous sponsor). It is the most popular racing series in the United States, drawing over 6 million spectators in 1997, averaging over 190,000 people for each race not including television audiences. The most famous event in the series is undoubtedly the Daytona 500, an annual 500-mile race at Daytona Beach, Florida. The circuit's second-biggest event is probably the Brickyard 400, an annual 400-mile race held at the Indianapolis Motor Speedway, the legendary home of the Indianapolis 500. NASCAR also runs the Busch Series, a stock car junior league, and the Craftsman Truck Series, a junior league where pickup trucks are raced. Together the two car-based series (Winston Cup and Busch Series) drew 8 million spectators in 1997, compared to 4 million for both American open-wheel series (CART and IRL). In 2002, 17 of the 20 US top sporting events in terms of attendance were NASCAR races. Only football drew more television viewers that year.

Fans of other racing series, such as Formula One, often have low opinions of the series and its fans. They regard the drivers, cars, and fans as interesting relics of less sophisticated times, with the restrictive regulations removing any possibility for technical innovation. Whilst it is undoubtedly true that stock car racing is less technically sophisticated than many other forms of motorsport, the relative equality of the machinery makes the racing closer and results much more of a test of driver and pit crew ability than more technically-oriented motor racing series that are often decided in wind tunnels and on CAD terminals well before any actual racing takes place.

Whilst the challenges of driving and setting up the cars around near-identical banked ovals are probably fewer than learning varied road circuits, the aerodynamic factors giving advantages to a tactically-savvy driver lead to interesting contests which bear some resemblance to some forms of track cycling. In particular the aerodynamics ensure that cars which are following each other both have less drag than either car alone. Therefore it is in the drivers' interests to cooperate in forming chains of cars with low drag. Yet a driver must at some point end cooperation in order to win the race. The combination of cooperation and non-cooperations leads to some very sophisticated strategic decision making.

See also: List of famous NASCAR drivers