Automobiles are self-propelled vehicles that operate on land, usually with four wheels and an internal combustion engine fueled by gasoline. Historically, automobiles have played a significant role in the development of modern society.

The first automobiles were steam-powered, but the internal combustion engine, invented by Dutch scientist Christiaan Huygens in the late 1600s, soon replaced them as the dominant form of transportation in the West. The French engineer Nicolas Joseph Cugnot built the first self-propelled vehicle (Paris, 1789), a heavy, three-wheeled carriage with a boiler that projected in front.

An automobile has a water-cooled, piston-type internal-combustion engine; it may be mounted in the front of the vehicle or be carried forward of the rear wheels. Passenger automobiles are usually fueled by gasoline, but diesel engines can be used for heavier vehicles such as trucks and buses.

Cars can be made of several different materials and designs, depending on the purpose for which they are designed. The most common construction materials are metals, plastics, and fiberglass.

The design and construction of automobiles is governed by the laws of physics, chemistry, and engineering. For example, the air intake and exhaust systems for gas-powered automobiles must meet federal pollution regulations.

Automotive manufacturing is an important industry in the world, producing a wide variety of products and services. It is a key component of the economy, providing employment to millions of people worldwide.

Despite its popularity, the automobile poses a major threat to our environment. The demand for oil and other petroleum-based fuels is increasing, and the emissions produced by automobiles can lead to air pollution problems. Should the demand for automobiles continue to grow at historical levels, environmental and energy issues of a magnitude yet unseen will face the world.