An electronic cigarette or "e-cigarette" is a battery-powered device that provides inhaled doses of nicotine by delivering a vaporized liquid nicotine solution. It is an alternative to smoked tobacco products, such as cigarettes, cigars, or pipes. In addition to nicotine delivery, this vapor also provides a flavor and physical sensation similar to that of inhaled tobacco smoke, while no tobacco, smoke, or combustion is actually involved in its operation.

An electronic cigarette usually takes the form of some manner of elongated tube, though many are designed to resemble the outward appearance of real smoking products, like cigarettes, cigars, and pipes. A common design is also the "pen-style", so named for its visual resemblance to a ballpoint pen.

Most electronic cigarettes are reusable devices with replaceable and refillable parts. A number of disposable electronic cigarettes have also been developed.

The legal status of electronic cigarettes varies by country.