Porvoo cathedral (Finnish: Porvoon tuomiokirkko, Swedish: Borgå domkyrka) is a cathedral of the Evangelical Lutheran Church of Finland in Porvoo, Finland. It was built in the 15th century, although the oldest parts date from the 13th century. It is the seat of the Diocese of Borgå, Finland's Swedish-speaking diocese. The cathedral is also used for services by the Porvoo Finnish-speaking parish, which is administratively part of the Diocese of Helsinki. The church had first become a cathedral in 1723, when the diocese of Viipuri (Viborg) (now the Diocese of Tampere) moved to Porvoo, after the Russian occupation of Viipuri.