Normann joins Pascal Gross, Josh Kerr, Mathew Ryan and Markus Suttner for Brighton's debut Premier League season and Chris Hughton is very happy with the signing.
"We are delighted that we've been able to bring Mathias to the club," manager Chris Hughton said.
"He is a talented and versatile young player, who already has good experience playing regular senior football in Norway."
"We are looking forward to welcoming him into the club, and his longer-term plan will be to break into the first-team group."