An ambulance is a vehicle designated for transporting people to or from a place of treatment for an illness or injury. An ambulance may travel from the site of an accident or injury to a hospital, from a hospital to a patient's home, or between two points of treatment (such as between a doctor's surgery and a hospital with specialist facilities).

The term ambulance is most commonly associated with the land based, motorized emergency vehicles seen throughout the world administering emergency care to those with acute illnesses or injuries, hereafter known as emergency ambulances. These are usually fitted with flashing warning lights and sirens in order to facilitate their movement through heavy traffic. It is these emergency ambulances that are most likely to display the Star of Life, which represents the six stages of prehospital medical care.

There are also several other types of ambulance used throughout the world. Probably the most common is the patient transport ambulance. These vehicles are not usually (although there are exceptions) equipped with a high level of equipment, and are usually crewed by staff with a lower qualification than those working on emergency ambulances. Their purpose is simply to collect patients from, or drop them off at, their place of medical treatment. In most countries, these are not equipped with flashing lights or sirens.

Throughout the world, the look of emergency and patient transport ambulances varies, although trucks, vans and station wagons are most commonly used. Other vehicles used as ambulances include buses, helicopters, airplanes, boats, and even hospital ships.