|King of Viken|
|Reign||946 - 963|
|Predecessor||Olaf I Geirstadalf|
|Successor||Harald II Greycloak|
|Issue|| Olaf II Tryggvasson|
|Father||Olaf I Geirstadalf|
The only son of Olaf I Geirstadalf, Tryggve succeeded to a troubled Viken. To the west in Hordaland his half-uncle Haakon I was attempting to wrest control of Viken for himself, unsuccessfully, but it still continued to stir up trouble. To the east in Gothenland other scions of the Fairhair dynasty were biding their time before they launched their own power grabs. And to the south Denmark was beginning to realise it could wield its own power in the north.
Tryggve was therefore kept relatively busy fending off the advances of his family yet he failed to secure an alliance with either Denmark or Svealand, a development which may have saved his kingdom. He instead continued the feud with Haakon I over the borderlands between the two Norwegian states, weakening both. When his cousin Harald II Greycloak successfully captured Hordaland, with Danish help, Tryggve was unprepared and Harald soon sought to reconquer all of Norway.
In summer of 963, having only just seen off the invasion of his uncle Ragnar Rykkel from Gothenland, Tryggve met Harald's army at the Battle of Túnsberg but was defeated and killed, whereupon Harald claimed the whole of Norway. The crowns were not however combined, Harald's rule was shaky in Viken and much reliant on Danish assistance.
Once Harald however had been betrayed by his supposed allies Viken passed to the Danish kings. Tryggve's son Olaf would however recapture the kingdom for a brief period (995-1000) during the reign of Sweyn Forkbeard.