A power tiller, also called a rotary tiller, rototiller, rotavator, or rotary hoe or plow, is a device used to cultivate soil. This machine has tines or blades that rotate to turn the soil by means of a motor. Power tillers can be self-propelled or an attachment behind a tractor. Pull-behind power tillers are usually powered by a connection to the tractor's engine, while self-propelled power tillers have their own motors. In some countries, a power tiller may also be a two-wheeled tractor, which may have other attachments and functions aside from cultivating soil.

The power tiller was invented in the early twentieth century to replace manual ploughing. Power tillers generally have small, one- to five-horsepower engines that usually take gasoline or a mixture of gasoline and oil. They are designed to propel forward slowly and to allow for the user to control the friction by raising and lowering the handlebars. As a safety feature, most power tillers can propel only forward and not backward.

Pricing for power tillers varies widely, depending on the size, horsepower, brand name, and quality. Most home improvement stores allow customers to rent power tillers for one-time usage. People who regularly maintain a large garden may find that simply purchasing a power tiller is more economical than renting one several times a year, however. Pricing may also depend on whether the machine is a front-tine or rear-tine tiller, the rear-tine variety often being the more expensive choice.

Power tillers ease the tough physical labor involved in turning, aerating, and cultivating soil. They have many uses besides simply turning soil, however, such as weeding, trench formation, top soil and fertilizer application, and garden or flower bed formation. The best power tillers are small in size and light weight for easy handling, and have a low center of gravity, adjustable speed, low fuel consumption, and adjustable handlebars.

Clearing the area of rocks, sticks, and other debris is a good idea before using the power tiller. Users should wear long pants, safety glasses, and ear protection when operating the tiller. Before refueling, users should wait until the tiller has cooled down.

Just like any other motorized lawn equipment, power tillers require a certain amount of maintenance. Emptying the fuel and following any other instructions from the manufacturer when preparing to store the tiller during the cold season is important to prolonging the tiller's lifespan. With a bit of care, a power tiller can last for a decade or even longer.