Seisen International School (SIS) is an all-girls, Catholic school located in Setagaya-ku, in Tokyo, Japan. Students and faculty from over sixty countries are represented at Seisen, with English being the main language of instruction. It offers the International Baccalaureate program for grades 11 and 12. It is accredited by the Ministry of Education, Culture, Sports, Science and Technology (Japan), New England Association of Schools and Colleges and the European Council of International Schools.