The maritime boundary between Finland and Sweden spans approximately 457 nautical miles and extends from the land boundary terminus in the Gulf of Bothnia to a tripoint with Estonia in the Baltic Sea. Initially the coasts are adjacent to one another but quickly curve to form the northern end of the Gulf of Bothnia. Due to areas where the gulf’s opposing coasts constrict, the Parties share three territorial sea boundaries, one adjacent to the land boundary terminus, one roughly mid-way through the gulf, and a third at the mouth of the gulf where its waters enter the Baltic Sea.

In an 1809 Peace Treaty, Sweden ceded control of Finland to the Russian Empire. This Treaty, along with a boundary description signed the following year, initially defined the maritime boundary between the two territories. This early portion of the maritime frontier was subsequently delimited by a series of coordinates recorded in a 1921 Convention.

The modern maritime boundary was delimited in an Agreement reached in 1972 that used a simplified version of equidistance that had been plotted using the straight baselines of both countries. It was later adjusted and extended, in 1994, when the Parties reached an agreement concerning Sweden’s economic zone, Finland’s fishery zone, and their overlapping entitlements to the continental shelf.

The “common point,” or tripoint, with Estonia in the Baltic Sea was established by virtue of a trilateral agreement reached in 2001.