Porvoo, one of Finland’s oldest cities, has a rich history dating back to the Stone Age. In ancient times, the Porvoonjoki River served as a vital trade route for the inland Tavastians. Early settlements developed along its banks, including villages such as Hattula (later Strömsberg), while trade flourished in Saksala, an early commercial center known as “the place of the Germans.” The name of the river, possibly Kukinjoki, is thought to originate from the medieval trading vessel known as a cog, which was widely used in the Baltic Sea.

Swedish colonization began in the 13th and 14th centuries following the Second Crusade against the Tavastians. Encouraged by the Catholic Church and the Swedish crown, settlers from Svealand arrived with incentives such as cattle, seeds, and tax exemptions. Porvoo received official town rights around 1380, making it the third town in Finland to do so, although some sources suggest an earlier founding date of 1347. In the centuries that followed, the town continued to evolve, including the relocation of the episcopal see in 1723 after Sweden’s loss of Vyborg.

Despite a devastating fire in 1760 that destroyed two-thirds of its buildings, Porvoo was rebuilt on its medieval foundations. The city played a pivotal role in Finnish history in 1809, when Alexander I of Russia declared Finland an autonomous Grand Duchy at the Diet of Porvoo. In the 20th century, Porvoo became a spiritual symbol of Lutheran unity through the Porvoo Communion. In 1997, the modern city was officially formed through the merger of the city and the rural municipality of Porvoo.