Van der Poel finished ahead of Danny van Poppel (Jumbo-Visma) and Andrea Pasqualon (Wanty-Gobert) on the 181km stage from Å to Leknes.
“It was a very hard race indeed," van der Poel said. "I couldn’t believe my eyes when I saw on my computer that our average speed was over 50km/h after three hours of racing.
"It was hard all day and I kind of liked it like that. At the end, I had to gamble that Jumbo-Visma would be closing the gap [on Stephen Cummings] as well as myself. There were a few other strong guys at the front.
"It was a difficult situation but with seven or eight kilometres to go, I already had in my mind that I was waiting for the sprint. I didn’t have many options so I was just waiting and trying to time my sprint perfectly.
"Many riders aren’t contending the GC anymore I think, because of this breakaway today. It’s gonna be very hard to defend the jersey.”
The pace was fast from the gun but the first move only came after 25km of racing when three riders made a short-lived escape.
Astana’s Magnus Cort and Amund Groendahl Jansen of Jumbo-Visma bridged across to the leading trio with Jansen taking the intermediate sprint.
With the peloton back together complexion of the race changed at the 64km mark when Stephen Cummings (Dimension Data) split the peloton leading to the formation of a 33-man group that included most of the favourites, including eventual stage winner van der Poel.
Already active from the start, Astana's Alexey Lutsenko made a move with 25km of road left, taking Lilian Calmejane (Total Direct Energie), Pascal Eenkhorn (Jumbo-Visma) and Cummings with him.
A few kilometres later it was all back together again with Cummings securing the mountains classification and Lutsenko winning the last intermediate sprint.
An attack led by Warren Barguil (Arkéa-Samsic) and Magnus Cort (Astana) was attempted but failed as van der Poel put on a show of strength to bring them back.
Cummings went again solo with less than 5km to cover and managed to stay ahead until 50 metres to go when van der Poel passed him ahead of van Poppel and Pasqualon.
