The Service Medal of the Order of St John is awarded to recognise both conspicuous and long service with the Venerable Order of St John, particularly in St John Ambulance, both in the United Kingdom and in a number of other Commonwealth countries and Hong Kong. The award was announced in the St John Ambulance Brigade General Regulations for 1895 and minted in 1899, though the first honourees had been selected the previous year.

The Order of St John, short for Most Venerable Order of the Hospital of Saint John of Jerusalem and also known as St John International, is a British royal order of chivalry constituted in 1888 by royal charter from Queen Victoria and dedicated to St John the Baptist.