An automobile, or car, is a wheeled motor vehicle for carrying passengers. It is usually powered by a petroleum-based internal combustion engine and uses a volatile fuel to create mechanical energy, which drives the wheels to turn the car forward or backward. It also has a number of systems designed to keep it stable and safe, such as brakes, steering, and suspension.

Automobiles are generally more comfortable and convenient than walking or riding a bicycle for long distances, can carry more people than a bicycle or bus, and can go places that public transportation (bus, passenger train, steam-powered, diesel-powered or light rail) cannot. Automobiles are available in a wide variety of styles and sizes, and have many applications. There are vehicles intended for general transportation, cargo, and special needs (such as fire, sanitary, mobile crane, autoclave or infantry fighting cars). Most modern automobiles have an internal combustion engine powered by gasoline, although some use other fuels, including diesel, kerosene, or electricity.

The development of the automobile was a milestone in world history, changing the way people live and work. The automobile made it possible for people to travel far from home, and to move around the country or even across the world. Automobiles are now the dominant form of personal transport, and are used to move three trillion miles each year.

In the early years of the twentieth century, the United States became the center for automotive innovation. Henry Ford innovated mass production techniques, producing the Model T runabout at a cost that was less than the average annual wage in 1912. This allowed automobiles to be affordable for middle-class Americans, and the concept of mass personal transportation was born.

After the end of World War II, the American automotive industry stagnated. Manufacturers funneled their resources to the rebuilding of America, and technology was incremental rather than revolutionary. The basic features that distinguish post-World War II models from the Model T were in place by the late 1920s: self-starting, closed all-steel body, hydraulic brakes, and syncromesh transmission.

Today, automobiles are manufactured in over a hundred countries and make up one of the largest industries in the world. They are a major source of air pollution, and contribute to climate change by emitting large amounts of greenhouse gases. In addition, the huge numbers of cars on the roads cause traffic congestion, which is bad for both the environment and the health of those who have to spend large parts of their lives stuck in slow-moving cars.

Automobiles are complex technical systems, and a great deal of research and development is needed to keep them evolving. Some of the latest advancements include computer-controlled engines, high-strength steel alloys, and new nonferrous metals. The automobile is an important part of the global economy, and its use varies widely by country. In the United States, the automotive industry is classified by the North American Industry Classification System code (NAICS). The NAICS database provides statistics on business establishments in all sectors of the economy.