The eastern border of Finland is at present the longest of all the borders between member states of the European Union and Russia, and certain parts of it represent one of the oldest national borders to be found anywhere in Europe, dating from the peace treaties of Tayssina and Stolbova in 1595 and 1617, respectively. One notable border in Europe that is older is that between England and Scotland, the first known mention of which is in documents from around 1237. In Early Modern times – from the first half of the 16th century to the Age of Revolutions – this eastern border served as the dividing line between the realms of Sweden and Russia, and its actual location varied with time on account of wars between these two nations and the peace treaties that followed them. In the discussion below we will examine the early history of the border mainly in terms of two questions: What physical form did the border take on in the Early Modern period, and was it guarded, and if so, for what reason?