A motorcycle or motorbike is a single-track, two-wheeled motor vehicle powered by an engine. Styles of motorcycles vary depending on the task for which they are designed, such as long distance travel, navigating congested urban traffic, cruising, sport and racing, or off-road conditions. In many parts of the world, motorcycles are among the least expensive and most widespread forms of motorised transport.

Motorcycles must be leaned in order to turn. This lean can be induced by a method known as countersteering, in which the rider turns the handlebars in the direction opposite of the desired direction of turn. In other words, press forward on the handgrip in the desired direction—press right to go right, press left to go left. This concept is counter-intuitive and often very confusing to novices—and even to many experienced motorcyclists.

Short wheelbase motorcycles, such as superbikes, can generate enough torque at the rear wheel and enough stopping force at the front wheel to lift the other wheel off the ground. These actions, if performed on purpose, are known as wheelies and stoppies respectively. If carried past the point of recovery the resulting upset is known as "looping" the vehicle.

Sportsbikes are fast, light, sleek motorcycles designed to give maximum performance for racing or spirited road riding. They are distinguishable by their racing style fairings and the rider's tipped-forward seating position. Some are called "race replicas" because of their connection to the racing category for production motorcycles known as Superbike racing.

Superbikes are large displacement super sportsbikes. They have characteristics similar to the smaller  sportsbikes. but are powered by larger engines that are usually sized around 800 cc to 1,200 cc.

Today, the Japanese manufacturers, Honda, Kawasaki, Suzuki, and Yamaha dominate the motorcycle industry, although Harley-Davidson still maintains a high degree of popularity in the United States.

Recent years have also seen a resurgence in the popularity of several other brands sold in the U.S. market, including BMW, KTM, Triumph, Aprilia, Moto-Guzzi and Ducati. Outside of the USA, these brands have enjoyed continued and sustained success, although Triumph, for example, has been re-incarnated from its former self into a modern world-class manufacturer. In overall numbers, however, the Chinese currently manufacture and sell more motorcycles than any other country and exports are rising. The quality of these machines is asserted to be somewhat lower than their Japanese. Additionally, the small-capacity scooter or moped is very popular through most of the world. The Piaggio group of Italy, for example, is one of the world's largest producers of two-wheeled vehicles.