St John's College was a private day and boarding school located in Southsea, Hampshire, England. It was founded by the De La Salle brothers in 1908. In May 2022, the Governors announced that the school would not re-open for the academic year starting that September, citing declining student numbers, under-investment and the impact of the COVID-19 pandemic as the causes. In August 2022, St John's College appointed administrators and went into liquidation. The head of the college at the time of closure was Mary Maguire.

Southsea is a seaside resort and a geographic area of Portsmouth, Portsea Island in the ceremonial county of Hampshire, England. Southsea is located 1.8 miles (2.8 km) to the south of Portsmouth's inner city-centre.