Gilgeous-Alexander, whose performance at the World Cup also helped the men's team secure a place at the 2024 Paris Olympics, is the second basketball player to win the award after Hall of Famer Steve Nash took the honours in 2005.
Gilgeous-Alexander beat Nick Taylor, who this year became the first Canadian in 69 years to win his national open, swimmer Summer McIntosh, hammer thrower Camryn Rogers and Connor McDavid of the NHL's Edmonton Oilers for the award.
Last NBA season, he averaged 31.4 points per game along with 5.5 assists and 4.8 rebounds with the Thunder and was named an All-Star for the first time in his professional career.
In 20 games this season, Gilgeous-Alexander is averaging a team-high 30.5 points per game, sixth best in the NBA.
Previously known as the Lou Marsh Trophy, the Northern Star Award is handed out annually by the Toronto Star newspaper and is voted on by a panel of Canadian sports journalists.
Past winners include Bayern Munich's Alphonso Davies (2020) former U.S. Open tennis champion Bianca Andreescu (2019) and decorated Olympic swimmer Penny Oleksiak (2016).