St John Ambulance is the name of a number of affiliated organisations in mostly Commonwealth countries which teach and provide first aid and emergency medical services, and are primarily staffed by volunteers. The associations are overseen by the international Order of St John and its priories.

Emergency medical services (EMS), also known as ambulance services or paramedic services, are emergency services that provide urgent pre-hospital treatment and stabilisation for serious illness and injuries and transport to definitive care. They may also be known as a first aid squad, FAST squad, emergency squad, ambulance squad, ambulance corps, life squad or by other initialisms such as EMAS or EMARS.