It was founded by the Religious of the Sacred Heart of Mary in 1955 to educate the children of overseas business, industrial, and diplomatic dynasties with a presence in the UK.

Situated on a 7-acre (2.8 ha) campus 12 miles (19 km) from central London, it is open to children of all faiths or none.

[1] It is part of a network encompassing nine countries and three continents, with sister schools in Paris, Rome, New York, Los Angeles and Colombia.

In 1979 it became the first school in the United Kingdom to fully adopt the International Baccalaureate programme as its main curriculum of instruction.

Marymount is an international school which caters to a diverse student population and incorporates aspects of both the American and British educational traditions.