Olsborg was constructed in 1502 by the squire Nils Ravaldsson from Åby (died 1505), after a recent Norwegian-Swedish rebel attack on Viken.
However most of Olsborg was destroyed shortly after, when the forces of Scandinavian monarch King Hans attacked during the Christmas party in 1504.
[1] [2] After the turmoil created by the dethronement of the Danish king Christian II, the Swedes returned, seized the area and reconstructed Olsborg's fortifications.
The brief Swedish rule of northern Bohuslän was administrated between 1523 and 1525 from Olsborg by the nobles Lars Siggesson (Sparre) (c. 1492-1554) and Ture Jönsson (Tre Rosor) (c.1475-1532) .
During Christian II's attempt to retake his throne, the part of Bohuslän under Swedish rule was attacked, and both Karlsborg and Olsborg were destroyed by Norwegian forces in December 1531.