Automobiles are four-wheeled vehicles designed primarily for transportation of passengers and sometimes cargo. Most automobiles are powered by an internal combustion engine using a volatile fuel. The modern automobile is a complex technical system, consisting of many subsystems with specific design functions. These include safety, passenger comfort options, performance on high-speed limited-access roads, and optimization of vehicle stability and handling under all operating conditions.

The development of the automobile revolutionized transportation in the United States and other parts of the world, changing the lives of the people who use it. It enabled people living in urban areas to travel to rural places, and people living in the country to move into cities, and allowed them to do so much more than they could before the advent of the automobile. It also opened new opportunities for business, leisure and entertainment activities.

The scientific and technological building blocks of the automobile go back several hundred years, but the car as we know it today first became widely available in the early 20th century. The earliest cars used steam, electricity or kerosene as their primary source of power. The steam engines were slow and required careful management to avoid overheating, while battery-powered electric cars had limited ranges and recharging stations were difficult to find. Gasoline-powered cars offered a middle ground.

Ransom E Olds introduced the large-scale production of affordable automobiles using an assembly line approach at his Oldsmobile factory in 1902. Henry Ford radically improved mass-production methods with the introduction of the Model T, which brought the car within reach of the common person. Several other companies entered the automotive market, including General Motors and Chrysler.

The modern automotive industry is dominated by manufacturers that make a variety of different models. These include sport utility vehicles, commercial trucks and vans, hatchbacks, sedans and coupes, convertibles, and station wagons. SUVs are a class of automobile that combines the towing capability of a pickup truck with the passenger-carrying space of a sedan. The automobile is the most important means of transportation in most developed countries, and has revolutionized many aspects of society.

Some cars have been specially designed for off-road driving, with features such as higher ground clearance, all-terrain tires, and increased suspension capacity. In addition, some automobiles have been designed for people who need to carry a large amount of cargo, or for special purposes such as fire fighting, medical emergencies and military use. These vehicles are often larger, heavier and more expensive than other types of automobiles.