The biggest deficit a team has ever overcome to win a Super Bowl is 10 points.
Flacco completed 13-of-20 passes for 192 yards, punctuating his outstanding first half with a 56-yard TD pass to Jacoby Jones with 1:45 left in the second quarter.
Flacco evaded a pass rush, stepped up in the pocket and lofted a pass downfield to Jones, who had to slow down his route in order to make a sprawling catch inside San Francisco's 10-yard line. Jones fell to the ground before scrambling to his feet, spinning from a defender and racing the rest of the way into the end zone.
San Francisco responded with an eight-play, 71-yard drive capped by David Akers' 27-yard field goal. It was the second field goal of the game for Akers, who also kicked a 36-yarder in the first quarter.
Flacco also threw touchdown passes to Anquan Boldin and Dennis Pitta while completing passes to seven different receivers in the first half. The Ravens, who will get the ball to start the second half, gained 241 yards of total offense and forced two turnovers in the first half.
San Francisco's first turnover was a costly one, as rookie running back LaMichael James lost a fumble at the Baltimore 25. Rookie linebacker Courtney Upshaw forced the fumble, which was recovered by Arthur Jones.
The Ravens took a 14-3 lead on the ensuing drive, as Flacco hooked up twice with Ed Dickson before finding Pitta for a 1-yard TD.
On the next play from scrimmage, Ravens star safety Ed Reed tied an NFL record with his ninth career postseason interception by picking off Colin Kaepernick. After Reed stole the ball, a group of players from both teams engaged in a scrum and penalties were called.
Instead of adding more points after Reed's pick, Baltimore eventually gave the ball back after trying a fake field goal but failing to get a first down.
Kaepernick completed 8-of-13 attempts for 139 yards in the first half while San Francisco tight end Vernon Davis had four catches for 72 yards.
Information from The Associated Press was used in this report.