An automobile is a self-propelled motor vehicle for passenger transportation that runs on four wheels and is powered by an internal combustion engine, usually fueled with gasoline, a liquid petroleum product. The automobile has become one of the most universal of modern technologies, with some 70 million vehicles sold worldwide each year. The history of the automobile is rich and varied, and its invention has profoundly shaped the course of human society.

Having your own car provides you with the freedom to move about when you want without having to rely on others or public transport, and you can save time by not having to wait around for buses or taxis. It also allows you to reach destinations that are not well served by public transportation, such as rural areas or remote sections of a city or town. Moreover, having your own vehicle enables you to live farther away from work, which can reduce your overall transportation costs.

The automobile revolutionized the economy by providing the basis for a new consumer goods-oriented society. It stimulated participation in outdoor recreation and created tourism-related industries, such as service stations and motels. It ended rural isolation and brought urban amenities, such as hospitals and schools, to country residents. It was one of the largest contributors to street and highway construction, and it was the lifeblood of many ancillary industrial enterprises, including steel and oil.

Early on, the automobile was a largely hand-built craft, with hundreds of small shops producing a few handmade vehicles at a time. The handful that made it to the era of mass production shared certain characteristics, namely the ability to produce their cars quickly and at reasonable cost. This was due in part to innovations, such as the assembly line and the use of mass-production techniques, by U.S. automaker Henry Ford, that revolutionized industrial manufacturing and allowed Ford, General Motors and Chrysler to dominate the market.

While automobiles have many social benefits, they also pose significant environmental and economic risks. They are the main source of air pollution and a major drain on dwindling world oil supplies, and they are responsible for the greenhouse gases that scientists say are driving global warming. The environmental impacts of automobiles can be mitigated to a degree by reducing their fuel consumption, emissions and waste production, as well as by encouraging use of alternative energy sources.

In the postwar era, automotive engineering was subordinated to questionable aesthetics and nonfunctional styling, which contributed to poor vehicle quality and high repair costs. In addition, the higher unit profits that Detroit made on gas-guzzling road cruisers came at the social cost of increased air pollution and a drain on dwindling world oil reserves. These factors led to the erosion of American market share and the penetration of foreign manufacturers of smaller, functionally designed cars that offer better fuel efficiency. They have been joined in the international market by Japanese models that have improved fuel efficiency even further.