Trailing 24-0 after 30 minutes, the Broncos (3-3) completely turned it around in the second half, outscoring the Chargers 35-0 the rest of the way to forge a tie with San Diego atop the AFC West standings.
Manning (24-for-30, 309 yards, one interception) connected with Demaryius Thomas on a 29-yard scoring strike to begin the comeback, later finding Eric Decker and Brandon Stokley on TD tosses.
The Broncos also added defensive touchdowns from Tony Carter on a 65-yard fumble return and Chris Harris on a 46-yard interception during the rally.
Phillip Rivers was picked off four times for San Diego (3-3), completing 25-of-41 passes for 242 yards with a pair of TDs in the loss.
The Chargers committed six turnovers overall.