International schools are private and public schools that promote education in an international environment or framework. Although there is no uniform definition or criteria, international schools are usually characterised by a multinational student body and staff, multilingual instruction, curricula oriented towards global perspectives and subjects, and the promotion of concepts such as world citizenship, pluralism, and intercultural understanding; most are private schools. Many international schools adopt a curriculum from programmes and organisations such as the International Baccalaureate, Cambridge International Education, European Baccalaureate, Edexcel, FOBISIA, International Primary Curriculum, or Advanced Placement. International schools often follow a curriculum different from the host country, catering mainly to foreign students, such as members of expatriate communities, international businesses or organisations, diplomatic missions, or missionary programmes. Admission is sometimes open to local students to provide qualifications for employment or higher education in a foreign country, offer high-level language instruction, and/or foster cultural and global awareness.

The first international school can be traced back to the International School of Geneva, founded in 1924 by Arthur Sweetser and Ludwik Rajchman with an emphasis on bilingual education (English and French). Later that year, the Yokohama International School was established in Yamate, Yokohama, Japan. These schools catered to children of expatriate families. These could include diplomats, missionaries, military members, business workers transferred to foreign office locations, etc.

An example would be children of American military personnel attending Department of Defense Dependents Schools (DoDDS).

At a conference in Italy in 2009, the International Association of School Librarianship came up with a list of criteria for describing an international school, including

However, educators disagree on what the exact criteria should focus on. Factors such as international history, culture, and perspective within the education curriculum make a school "international". Although students' nationality plays a big part, how the education is delivered is just as important.

While English-language international schools are the most numerous, many international schools teaching primarily in other languages exist. For instance, there are 140 German schools abroad which are accredited and partly funded by the German federal government through the Central Agency for German Schools Abroad (Zentralstelle für das Auslandsschulwesen) and the Federal Office of Administration (Bundesverwaltungsamt) which is part of the German government's Federal Ministry of the Interior (Bundesministerium des Innern). According to the German Foreign Office, the government's support of these schools "helps to overcome cultural barriers, to convey a modern, diverse image of our country and to strengthen German language skills in other countries."

Other examples of non-English international schools include:

Curricula in English-language international schools are most often based on education in the United Kingdom, education in the United States, or curricula specifically designed for international schools, such as the International General Certificate of Secondary Education or the IB Diploma Programme. These international curricula are committed to internationalism, developing the global citizen, providing an environment for optimal learning, and teaching in an international setting that fosters understanding, independence, interdependence, and cooperation.