Peyton Manning threw for 204 yards and a score in his ninth consecutive win against Baltimore, the first with the Broncos (11-3).
Down 10-0 late in the first half, the Ravens had a first-and-goal at the Denver 4 when Harris stepped in front of Anquan Boldin, picked off a pass by Joe Flacco and sprinted down the right sideline en route to the longest regular-season interception return in Broncos history.
The Ravens (9-5) were playing their first game under offensive coordinator Jim Caldwell, who replaced the fired Cam Cameron.
Baltimore's offense sputtered in the first half, gaining only 119 yards and committing two turnovers that led to 10 Denver points. It was the third straight loss for the Ravens.