Tyler Seguin -- one of the NHL's biggest stars -- knelt for the national anthem before Dallas' game against Las Vegas on Monday ... joining three others on the ice for the protest.
It all went down at the Rogers Center in Edmonton ... where Seguin, his Stars teammate Jason Dickinson, and Golden Knights players Ryan Reaves and Robin Lehner all dropped to one knee in the pregame ceremony.
The two Dallas players were flanked by the two Golden Knights at one of the ice's blue lines -- and the quartet stayed kneeling for the Canadian national anthem as well.