A motorized tricycle, motor trike, or motortrycle is a three-wheeled vehicle based on the same technology as a motorcycle, and powered by an electric motor, motorcycle, scooter or car engine.

Depending on the design of the vehicle, a motorized trike may be categorized as a motorcycle, motor scooter, or simply the three-wheeled counterpart to a motorized or electric bicycle. The main difference between a motorcycle trike and a scooter trike is that motorcycles are sat on in a "saddle"-style seating (as with a horse), with the legs apart, and motorcycles have manual transmissions. Scooters have a "step-through" seating style, in which the driver sits on a more chair-like seat, with the legs together; as well, scooters have automatic transmissions. Laypersons often associate the engine size as a dividing line between motorcycles and scooters,^{[citation needed]} since a typical scooter has a small 50 cc engine, but scooter engines can also be as large as 650cc as used in the Suzuki Burgman.

Motorcycles with sidecars are not usually considered tricycles. It can be harder to categorize three-wheeled automobiles. While some early prototype automobiles were steam tricycles, three-wheeled cars such as the Morgan 3-Wheeler are often classified as cars rather than motorcycles. Generally, the motorcycle classification will require passengers to sit behind the driver, whereas in the car classification, at least one passenger is able to sit abreast to the driver.

The motorized tricycle had quite a boom period at the end of the 19th century. Early engines weren't as compact or lightweight as modern ones, and clutches, and electric ignition were still new ideas being incorporated. Given this, the tricycle offered a better platform to add an engine to than a bicycle. The addition of engines to tricycles was covered in a motor supplemenet to Cycling magazine in 1899, from which the following are taken :

There were many more makes, and then variations with tandem seating to allow a passenger. Prices were typically £70 to £85, so they were not budget transport - though a lot cheaper than the early cars. Most had no gears and no clutch (the Pennington being the exception), so you had to pedal to start them. Other makers had twin wheels at the front and a single at the back, allowing a passenger to be carried in comfort right at the front - away from the noise and smoke of the engine, but vulnerable in the event of a collision.

A motorized tricycle's wheels may be arranged in either configuration: delta or reverse (tadpole). A delta trike has one wheel in front and two in back, and the reverse or tadpole trike has two wheels in front and one in back. Occasionally, rear wheel steering is used, although this increases the turning circle and can affect handling (the geometry is similar to a regular trike operating in reverse, but with a steering damper added).

Tadpoles are more stable under braking and more likely to slide instead of roll; front braking hard on a delta requires the vehicle to steer almost straight to avoid tipping. The balance of friction patches and rolling resistance also means that tadpoles tend to oversteer and deltas understeer.

Motor trikes are attractive for those with mobility or balance problems.