ESPN's Adam Schefter reported that the extension is worth $96 million over six years and includes $45 million in guaranteed money.
ProFootballTalk reported that Tannehill's signing bonus is $21.5 million.
Tannehill just completed his third season with the Dolphins since being selected in the first round of the 2012 draft out of Texas A&M.
Last season he completed 66.4 percent of his passes for 4,045 yards with 27 touchdowns and 12 interceptions.
“He is a proven quarterback in this league that combines a talented skillset with work ethic, passion, toughness, and a team first mentality,” Dolphins general manager Dennis Hickey said, according to the Palm Beach Post. “We are committed and believe in Ryan as our quarterback for the long-term and we are excited to be able to sign him to this extension.”
Tannehill is the first quarterback of the 2012 draft class to sign a long-term extension.
Last season the Dolphins went 8-8 and finished in third place in the AFC East.