St Johns is a locality southeast of Kapunda in the northern Barossa Valley, South Australia. Originally a private subdivision of the hundred of Belvidere, the boundaries of the locality were formalised in 2000 and the name formally adopted based on long-established use.
The foundation stone for the St John the Evangelist church was laid on 2 April 1850, however the building was not completed until 30 April 1854. A school was opened in 1859, run by the Sisters of St Joseph after 1868. From 1897, the school became a reformatory for girls until it closed in 1909.