Marymount International School is a private day and boarding school for girls in Kingston upon Thames, London, England. Founded by the Religious of the Sacred Heart of Mary in 1955 it is open to children of all faiths or none. It is situated on a 7-acre (2.8 ha) campus 12 miles (19 km) from central London.

Marymount is a fully accredited IB World School and is also accredited by the Council of International Schools and the Middle States Association of Colleges and Schools (USA). It is a member of the Girls' Schools Association. As an international school it attracts children from expatriate families and also accepts local students.

Marymount International School was founded in 1955 by the Religious of the Sacred Heart of Mary to educate children from the business and diplomatic community. 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 follows the International Baccalaureate's Middle Years Programme (MYP) for girls aged 11 to 18, and the Diploma Programme for the last two years.

The school achieves academic results that are above the global average. The class of 2022 averaged 37 points on the IB Diploma, with 33% of graduating students scoring 40 points or above, typically only achieved by approximately 5% of students worldwide. In 2011, 20% of IB Diploma candidates received a score of 40 points or higher.

Marymount is an international school which caters to a diverse student population and incorporates aspects of both the American and British educational traditions. The British-style blazer is part of the prescribed uniform and the house system is an integral part of student life. American nomenclature for year groups is used, meaning there is no "sixth form" as the final year of secondary education (age 17/18) is grade 12 rather than year 13 ("Upper Sixth"). Student leaders are elected into a "Student Council" and the head of the council is known as a president rather than head girl. In the middle of the school year, grade 10 and 11 students are elected into the National Honor Society. A formal graduation ceremony is held at the end of the year to farewell grade 12 students.

The four houses are named after founders of the Religious of the Sacred Heart of Mary.

• St Jean
• St Constance
• St Felix
• St Croix

Boarding is an option to all students and about a quarter of the student body are boarders. They are housed in four main halls and cared for by houseparents and a resident nurse. Younger boarders usually reside in triple rooms and older students are allocated either double or single rooms.

As a Catholic school, spiritual life is an important aspect of student life. Students are expected to attend chapel services and invited to actively participate. A Sacrament of Confirmation is held every two years.

Students may also take part in community service projects through exchange programmes with its sister schools in the RSHM international network of schools.

• Elizabeth Gill Lui (b. 1951) - American photographer
• Gail Zappa (1945-2015) - wife of Frank Zappa

• School Website
• [2]RSHM International Network of Schools
• Profile on MyDaughter
• Profile on the ISC website
• ISI Inspection Reports