Stamkos, who was the first overall pick of the 2008 NHL Draft, takes over the captaincy for Martin St. Louis, who was shipped to the New York Rangers in a blockbuster trade for Ryan Callahan hours before Wednesday's trade deadline.
"Steven Stamkos was destined to be the leader of our team," head coach Jon Cooper said. "The fact that it's happening now just puts us one step closer to achieving our ultimate goal and that is trying to win the Stanley Cup."
The 24-year-old registered 14 goals and nine assists in 17 games this season before suffering a broken right tibia in a 3-0 loss to Boston on Nov. 11. His injury prevented him from traveling to Sochi to represent Team Canada in the 2014 Winter Olympics.
Stamkos won the Maurice "Rocket" Richard Trophy as the league's top scorer in both 2010 and 2012. No NHL player has scored more goals than Stamkos since the start of the 2009-10 season. He was also selected to play in the NHL All-Star game in 2011 and 2012.
The Ontario native ranks third all-time in franchise history for goals, power- play goals, and game-winning goals. He is also fourth all-time in points.
Defenseman Eric Brewer will take over Stamkos' previous role as full-time alternate captain, while defenseman Matt Carle and forward Nate Thompson will share alternate duties.