The Diet of Porvoo (Finnish: Porvoon maapäivät, or unhistorically Porvoon valtiopäivät; Swedish: Borgå lantdag; Russian: Боргоский сейм), was the summoned legislative assembly to establish the Grand Duchy of Finland in 1809 and the heir of the powers of the Swedish Riksdag of the Estates. The session of the Diet lasted from March to July 1809.
During the Finnish War between Sweden and Russia, the four Estates of Russian-occupied Finland (nobility, clergy, burghers and peasants) were assembled in Porvoo (Borgå) by Tsar Alexander I, the new Grand Duke of Finland, between 25 March and 19 July 1809.
Finnish historians disagree on whether the Diet of Porvoo was the first meeting of The Estates in the history of Finland or a traditional lantdag where the eight easternmost regions of Sweden were transferred under the authority of the Emperor of Russia. According to the interpretation of the Finnish constitution born later in the 19th century, the state of Finland was born at the Diet of Porvoo. The historian Henrika Tandefelt claims that the Porvoo Diet could not have been a riksdag ("meeting of the state") as there was no state to speak of at the time.
The acting Governor-General of Finland Göran Magnus Sprengtporten made a plan for the government of Finland, which the Emperor confirmed on 1 December 1808. The delegation of the Estates in Finland had already sworn their loyalty to the Emperor in Saint Petersburg in the autumn. The delegation was told that the Emperor would be assembling a diet. Sprengtporten was given the task of preparing for the diet. The Estates received an invitation to attend the diet in Porvoo on 1 February 1809.
The decision to hold the diet in Porvoo was influenced by the still ongoing Finnish War and that the cities of Turku and Hämeenlinna were located too far away from the border to Russia. There had been a large fire in Helsinki in the previous year and there were no suitable premises for the diet in the city, neither were there any in Loviisa. So Porvoo was chosen as the location of the diet, which was opened at the Porvoo Cathedral. The main lecture hall of the Borgå Gymnasium acted as the main hall of the diet. The estate of the clergy also worked at the gymnasium. The estates of the nobility and the bourgeoisie were assembled at the Porvoo Town Hall and the estate of the peasants at the house of the lawspeaker Anders Fabian Orraeus.
The central event at Porvoo was the sovereign pledge and the oaths of the Estates in Porvoo Cathedral on 29 March. All of the Estates swore their oaths of allegiance, committing themselves to accepting the Emperor as Grand Duke of Finland as the true authority and to keep the constitution and the form of government unchanged. Alexander I subsequently promised to govern Finland in accordance with its laws and let the Finnish keep their religion and rights. This was thought to essentially mean that the emperor confirmed the Swedish Instrument of Government from 1772 as the constitution of Finland, although it was also interpreted to simply mean respecting other, "subordinate laws" - existing codes and other statutes.
The diet had required that it would be convened again after the Finnish War, which separated Finland from Sweden, had been concluded. On 17 September, the conflict was settled by the Treaty of Fredrikshamn, but it would take five decades for the Finnish Estates to be called again.
The Finnish translation of the sovereign's pledge given by Alexander I in old-style Finnish read as follows:
"Me Alexander I... Suuri Ruhtinas Suomen maasa... : Wakutus-Kirja... Annettu Borgåsa sinä 15/27 päiwänä Maaliskuusa 1809."
(ME ALEXANDER I., Jumalan Armosta, Kejsari ja Itsewaldias yli koko Ryssänmaan. Suuri Ruhtinas Suomen maasa Teemme tiettäwäxi: Että sitte kuin ME Sen Korkeimman edeskatsomisesta olemma ottanet Suuren Ruhtinan maan Suomen hallituxemme ala, olemma ME tämän kautta tahtoneet wahvistaa ja kiinittää Maasa olevan Christillisen Opin ja perustus- lait niin myös niitä wapauxia ja oikeuxia, kuin kukin Sääty nimitetysä Suuresa Ruh- tinan maasa erinomattain, ja kaikki sen Asuwaiset yhteisesti, niin ylhäiset kuin alhaiset tähän saakka Constitutionin eli säättämisen jälkeen owat nautinneet: Lupaamme myös pitää kaikkia niitä etuja ja asetuxia wahwana ja järkähtämättämänä heidän täydellisä woimasansa. Suuremmaxi wisseydexi olemma ME tämän Wakutus-Kirjan MEIDÄN omalla kädellämme ala kirjoittaneet. Annettu Borgåsa sinä 15/27* päiwänä Maalis- Kuusa 1809.
Pääkirja on korkiammasti omalla kädellä alakirjoitetu
"We Alexander I... Grand Duke in Finland... Pledge... Given in Borgå on the 15th/27th day of March in 1809."
(WE ALEXANDER I, by the Grace of God, Emperor and Autocrat over the entire country of Russia, Grand Duke in Finland, do hereby make it known: That as WE by the providence of The Highest One have taken the Grand Duchy of Finland under our government, have WE hereby wanted to strengthen and fasten the Christian doctrine and constitutional laws in the country, as well as those liberties and rights as the each estate in the aforementioned Grand Duchy, and all its inhabitants in general, the nobles along with the commoners have thus far enjoyed under the Constitution: We also promise to upkeep all these privileges and statures in their full authority. For greater confirmation have WE signed this pledge by OUR own hand. Given at Borgå on the 15th/27th day of March in 1809.
The pledge has been signed by own hand
The Diet of Porvoo had participants from different estates as follows:
Nobility: 75 representatives, chairman lantmarskalk count Robert Wilhelm De Geer.
Clergy: 8 representatives, chairman bishop of Turku Jakob Tengström
Burghers: 20 representatives, chairman merchant Kristian Trapp, Turku