Team vice president and general manager Steve Yzerman announced the deal Tuesday. The 21-year-old Stamkos was a restricted free agent. The team did not announce the terms.
The Markham, Ontario, native played in all 164 games during the previous two seasons for the Lightning, leading the NHL with 96 goals. He has also recorded 186 points and 41 power play goals while averaging more than 20 minutes of ice time per game during that span.
Last season Stamkos registered 45 goals and 91 points with 17 power-play goals.
He was the No. 1 overall pick in the 2008 draft.