Katedralskolan i Åbo (Cathedral School of Abo), Turku

The Cathedral School of Abo, located in Turku's Old Great Square, is the Swedish-language upper secondary school in the city. It is regarded as Finland's oldest institution of learning, with roots tracing back to 1276. Initially established to educate boys destined for the Church, the school’s original building was within the walls of the Turku Cathedral. Notably, Mikael Agricola, who is credited with founding Finnish literature, served as headmaster from 1539 to 1548.

When the Royal Academy of Turku, now the University of Helsinki, was founded in 1640, the senior part of the Cathedral School became part of the new university, while the junior levels evolved into a "trivial school." Turku Cathedral School graduates were automatically eligible for admission to the Royal Academy.

After the Great Fire of Turku in 1827, the current schoolhouse was built. By 1830, Turku also established a gymnasium, a higher secondary school, which led the Cathedral School to become a preparatory institution. Reflecting this change, it was renamed Higher Elementary School in 1840. In the 1872 education reform, the school merged with the gymnasium to become the Swedish Classical School of Turku.

In the 1970s, further consolidation occurred, and the school was renamed once again to its historical title, the Cathedral School of Abo. Since 1977, it has operated as a three-year upper secondary school following the introduction of the comprehensive school system in Turku.