Fortier was selected 4th overall in the 2016 Quebec Major Junior Hockey League (QMJHL) entry level draft by the Baie-Comeau Drakkar.

[1][2] On June 23, 2018, the Lightning selected Fortier with the 59th overall pick in the 2nd-round of the 2018 NHL Entry Draft.

Fortier recorded 26 goals and 33 assists during his draft year with the Baie-Comeau Drakkar.

[5] On November 30, 2021, Fortier made his NHL debut with the Lightning against the St. Louis Blues at the Enterprise Center.

[6] On June 21, 2023, the Lightning re-signed Fortier to a one-year, two-way contract.