St. Julian's School is a private British international school, located in Carcavelos, Cascais Municipality, on the Portuguese Riviera, in the Greater Lisbon region. It is housed at Quinta de Santo António, a historic Pombaline quinta (estate) near Carcavelos Beach.

St. Julian's is a British international private school located in the parish of Carcavelos e Parede, in Cascais, close to Lisbon, Portugal. The school takes its name from São Julião da Barra Fortress, overlooking nearby Carcavelos beach, originally erected in the mid-16th century to keep the British, among other raiders, out of the Tagus estuary.

The school opened on 24 November 1932 in the buildings, including residential palace, of the 18th-century estate founded by José Francisco da Cruz, treasurer to King D. José I. In the 2022/23 academic year, the school celebrated its 90-year anniversary.

In 1932, Mrs Bucknall OBE, who had been connected to the Parents’ National Education Union (PNEU), took the first steps towards the creation of an English-speaking School. Mrs Bucknall’s vision and perseverance were behind the many initiatives that led to the creation of St. Julian’s. With great determination, she organised meetings with the British community and contacted PNEU for assistance and advice. Serendipitously, Mrs Franklin CBE, a committee member of the PNEU was coming to Portugal on a short visit that year, during which she would be giving lectures on the aims of the PNEU. Mrs Franklin’s assistance proved to be invaluable in setting up the innovative pedagogy espoused by the fledgling school.

A committee was formed to examine the legal and financial aspects of founding a School and to find suitable premises. Mr Etherington-Smith, Mrs Bucknall, and others were elected to this committee. As the first Chairman of the Board, Mr Etherington-Smith successfully guided the School until he departed for England in 1944.

The committee inspected several properties aiming to find a suitable building. At the time, there was a serious outbreak of typhoid fever in Carcavelos, and the Founders feared that some of the properties being inspected could be contaminated.

In the first decades of the 20th century, Carcavelos was home to one of the stations of the Eastern Telegraph Company (ETC), the largest communications cable company in the world. Underwater cables were the links of that era’s first information highway. The cable installed in Carcavelos connected Europe to Africa. Its maintenance and operation required the services of specialised workers. A large group came from the UK and settled in the region. Major Montgomery, Manager of the ETC at Quinta Nova, generously offered a part of its facilities for the establishment of the School.

The support and recommendations provided by the British Ambassador, Sir Claud Russell, were of great importance during this period. In his role as Honorary Chairman, he was present at the St. Julian’s inaugural party, which was held on 24 November 1932. This date is now celebrated every year as Founders Day.

St. Julian's has just over 1,200 students, from age three to age 18.

The school is divided into three sections:

• The English Section which runs from Nursery (age 3) to Year 13 (age 18).  Students broadly follow the National Curriculum for England leading to IGCSEs in Year 10 and 11 (Key Stage 4) and the International Baccalaureate in Years 12 and 13. The English Section is further divided into the Primary Section: Pre-Prep School (Nursery and Reception), Prep School (Years 1 to 6) and Secondary Section (Years 7 to 13).
• The Bilingual Section where the language of instruction is in English and Portuguese.  This runs from 1º Ano (age 5) to 9º Ano (age 15). After 9º the students transfer into Year 11 of the Secondary Section and complete a series of IGCSEs over one year in preparation for the IB Diploma Programme in Years 12 and 13.

St. Julian's is run by a not-for-profit association, whose 50+ members, as trustees, appoint the board of governors. The board in turn appoint the head and bursar.

St. Julian's School is jointly accredited by the Council of International Schools (CIS) and the New England Association of Schools and Colleges (NEASC). The head is a member of the Heads' Conference (HMC). The school is also a member of the Council of British International Schools (COBIS).

Just under half the students at St. Julian's are Portuguese, with British the next largest nationality, and more than 40 other countries represented.

• Paula Rego, artist
• Daniela Ruah, actress

• St. Julian's official website
• St. Julian's School IB information
• HMC entry for St. Julian's School