Porvoo (pôrˈvō) [key] or Borgå bôrˈgō, city (1996 pop. 21,313), Southern Finland prov., S central Finland, on the Gulf of Finland at the mouth of the Porvoonjoki River. It is an export center for forest products and has plywood and cellulose mills, breweries, and a publishing industry. A trade center in the early Middle Ages, it was chartered in 1346, which makes it the second-oldest town in Finland. In 1809, Alexander I of Russia granted Finland a constitution at Porvoo, opening the diet there in the cathredral, parts of which date to the 13th cent. Most of the population is Swedish-speaking. The home and grave of the Finnish national poet J. L. Runeberg is in Porvoo.