A fire apparatus, fire engine, fire truck, or fire appliance is a vehicle designed to assist in fighting fires by transporting firefighters to the scene and providing them with access to the fire, along with water or other equipment. In some areas, the terms fire engine and fire truck represent different types of firefighting apparatus.

A modern fire engine is usually a multi-purpose vehicle carrying paid firefighters or volunteers and equipment for a wide range of firefighting and rescue tasks. Therefore, most fire engines carry equipment such as ladders, pike poles, axes and cutting equipment, halligan bars, fire extinguishers, ventilating equipment, floodlights, hose ramps, self-contained breathing apparatus (SCBA), and general tools. Many fire appliances are based on standard truck or lorry models with heavy duty suspensions, brakes, tires, alternator, transmission and cooling systems; audible and visual warnings such as sirens, horns, and flashing lights; and a two-way radio.

The fire engine may have several methods of pumping water onto the fire, such as passing water obtained from a fire hydrant through hoses or using a pumping "cannon" (also known as a monitor or deck gun); some trucks have an onboard water reservoir. Some fire engines may carry ladders to gain access to fires occurring in high-rise buildings and remove casualties, or hooks used to pull walls away to expose hidden fire or break windows. In some regions, a rescue unit is an EMS truck with tools to carry out technical rescues of people from traffic collisions or structural collapses.