It's tricky to name just one Norwegian national hero of all time, the country is full of them. WWII alone made them a heroic nation 'cause it's the country that lasted longer than
cheese eating surrender monkeys who lasted 42 days instead of 62!
They are also a sporty nation whose popular heroes can be found at the
cross-country skiing scene - nothing is more Norwegian than a bunch of asthmatic cross-country skiers in the woods with icy snot, or nothing is as erotic (from a man's POV) as in the mass start
competition of women's skate skiing on an uphill route; a queue of heavily panting women in a wide crotch position.
One of the quietest national heroes must be the cod who fought against German occupiers in the resistance movement.
Writer Knut Hamsun was awarded the Nobel Prize in Literature in 1920 and definitely one of Norway’s national heroes, his breakthrough work was "Hunger." He was also known as an avid fisherman but he became unpopular right after the War at an older age when he
accidentally caught the aforementioned resistance cod by using a heavy duty rod and a braided line - he could've released the hero fish but Knut was too hungry for it...
The icing on the cake is, of course, Vidkun Quisling who was the Führer of Norway from 1942 to -45 until he died suddenly of acute complications from nickel allergy and lead poisoning.