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, water or other equipment. In some areas, the terms fire engine and fire truck represent different types of fire fighting apparatus.

A modern fire engine is usually a multi-purpose vehicle carrying professionals and equipment for a wide range of fire-fighting 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, breathing apparatus (BA) 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"; some trucks have onboard water reservoir. Some fire engines have ladders to gain access to fires occurring in high buildings and remove casualties; hooks used to pull walls away to expose hidden fire or break windows. A rescue unit is an EMS (Emergency Medical Services) truck with tools to do technical rescues of people from car accidents or building collapses.

Fire departments covering large metropolitan areas have specialist appliances for dealing with hazardous material spills. Some fire departments may utilize fire boats or airplanes. A paramedic engine carries first responder firefighters, paramedics or EMTs to medical emergencies.