The German club confirm the deal on their website and say they have signed a three-year deal with Grondahl who is set to take over from Paul Drux, who has been forced to bring down the curtain on his career due to injury problems.
"It feels fantastic. It is a great honor to play for such a fantastic club with so many great players such as Mathias Gidsel, Lasse Andersson and many more", says Grondahl to the website, referring to the team's Danish stars.
"My primary goal is always to win everything. Right now, Füchse has the opportunity to win both the German championship and the Champions League. That will also be my goal for the coming seasons. Hopefully we can do it together and play handball that entertains."
Grondahl has played in the Champions League for four seasons and in the European League for one year. Most recently he also represented with GOG in the latter competition where they bowed out of the quarter-final against Flensburg-Handewitt.
Grondahl made his debut for the Norwegian national team at the age of 19. He now has 52 international matches to his name, in which he has scored 160 goals.