Tryggve Olafsson (Old Norse: Tryggvi Óláfsson; Norwegian: Tryggve Olavsson; born 928 in Ringerike – died c. 963 in Sotnes, Bohuslän, Västra Götaland, Sweden) was the king of Viken, Norway (Vingulmark and Rånrike). Biography. Tryggve Olafsson was the son of Olaf Haraldsson, king of Vestfold and Vingulmark, and grandson of King Harald Fairhair. According to the Heimskringla, Tryggve performed Viking expeditions in Ireland and Scotland. In 946 King Haakon I of Norway went north, and set Tryggve to defend Viken against his enemies in the south.
https://en.wikipedia.org/wiki/Tryggve_Olafsson