Broncos officials and Manning appeared at a news conference in Denver to announce the quarterback had signed a contract with the Broncos. The deal is reported to be for 5 years and valued at $96 million.
Manning said the Broncos were "a great fit" for him.
"I'm thrilled to be here," he said. "I'm looking forward to meeting my new teammates and doing whatever I can to help this franchise win another Super Bowl."
Manning played 13 seasons with the Indianapolis Colts, setting nearly every team passing record, but he missed all of 2011 because of a series of neck injuries.
The Colts, who have the No. 1 overall draft pick this year, released Manning March 7 and several teams immediately expressed interest in signing Manning as a free agent.
Manning sent a message to Broncos Executive Vice President John Elway, a Hall of Fame quarterback, Monday saying he'd decided on Denver.
"My goal is to make Peyton Manning the best quarterback to play the game," Elway told the news conference. "He's a guy that will make our football team better, just because of the type of person he is."
Manning started every game in his 13 playing seasons with Indianapolis, leading the club to 11 playoff appearances and a Super Bowl title after the 2006 season. An 11-time Pro Bowl selection, Manning has passed for 54,828 yards and 399 touchdowns in 208 regular-season games.
Denver will allow Manning to wear the No. 18 jersey. That number was retired in 1963 when quarterback Frank Tripucka left the Broncos. Tripucka was the quarterback in Denver for the first three seasons of the team's existence.