Baltimore quarterback Joe Flacco completed a last-minute 70-yard touchdown pass that helped the Ravens stun the Denver Broncos, while the San Francisco 49ers dominated the Green Bay Packers' defence to book a spot in the AFC title game.
Flacco's pass came with 31 seconds left to force overtime, and Justin Tucker kicked a 47-yard field goal to clinch a 38-35 win and dump Denver, the Super Bowl favourites, out.
San Francisco led Green Bay 24-21 at half-time but in the second half the Packers' defence was all at sea against 49ers quarterback Colin Kaepernick, who ran for a quarterback play-off record 181 yards. The hosts won 45-31. They will now play Atlanta, who snatched a 30-28 win over Seattle.
While Flacco's pass will go into Ravens folklore, his opposing quarterback Peyton Manning will be left to rue the overtime interception which led to the winning field goal.
"Our team is so confident and everything went against us," said retiring Ravens linebacker Ray Lewis, "but we found a way to come here together and we're leaving together."
This game, the longest since the Browns beat Cleveland 23-20 in 1987, was an all-time classic, as was Flacco's touchdown pass.
On third-and-three from his 30-yard line with 41 seconds and no timeouts left, Flacco bought time in the pocket and saw Jacoby Jones sprinting down the right sideline into double coverage.
Defensive back Tony Carter slowed up and let Jones streak by him before safety Rahim Moore got under the pass and allowed Jones to tie the game.
In overtime, Manning, moving to his right, threw back across the field and was intercepted by Corey Graham to allow Tucker's winning kick and give the few Ravens fans sat among the home crowd something to smile about.