St John Ambulance Ireland (SJAI), previously known as the St John Ambulance Brigade of Ireland, is a charitable voluntary organisation in Ireland. For constitutional reasons it is not a full member association of the Venerable Order of Saint John and the international St. John Ambulance movement, but rather is classed as an "associated body". The organisation is dedicated to the teaching and practice of medical first aid. It is engaged in first aid training to the public, providing first aid and ambulance cover at public events, patient transport and community services.

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.