"As an organization, we truly feel that Miro has just scratched the surface of his ability and will be in the Norris Trophy discussion for years to come," general manager Jim Nill said.
The Stars selected Heiskanen with the third overall pick in the 2017 NHL Draft. He has 95 points (28 goals, 67 assists) in 205 games, including 27 points (eight goals, 19 assists) in 55 games last season.
During Dallas' run to the 2020 Stanley Cup Final, Heiskanen notched 26 points in 27 games, the fourth-most by any defenseman during a playoff year in NHL history.
The 21-year-old is now the sixth-highest-paid defenseman in the league, trailing just Alex Pietrangelo, P.K. Subban, Roman Josi, Drew Doughty and Erik Karlsson.