Financial terms were not disclosed.
Landeskog, 20, scored eight goals and had nine assists last season for the Avalanche. He was the second overall selection in the 2011 NHL Draft, and won the 2011-12 Calder Memorial Trophy as the NHL's rookie of the year.
"Gabe is and will continue to be a large part of the foundation of this hockey team for many years to come," said Avalanche Executive Vice President of Hockey Operations Joe Sakic. “Signing our captain to a long-term extension demonstrates the commitment of Stan and Josh Kroenke to this franchise and to our fan base. In just two seasons, Gabe has already proven to be a great asset to our organization both on and off the ice. The fact that he has agreed to a long-term deal shows that he believes in this team, his teammates and the direction of this franchise moving forward."