Österbotten County, Österbottens län, or Pohjanmaan lääni, was a County of Sweden from 1634. In 1774 it was renamed Vasa County (Vasa län or Vaasan lääni) and Uleåborg County (Uleåborgs län/Oulun lääni) was split off. In 1808 when it was ceded to Russia. It was continued as an administrative entity of the Grand Duchy of Finland until 1917, and following this as a County of Finland until the large scale reorganization in 1997 when it was merged into the province of Western Finland.