Santa Clara, California - The San Francisco 49ers and the Kansas City Chiefs set up a Super Bowl rematch on Sunday after battling through to the NFL championship showpiece on a dramatic day of playoff action.

Taylor Swift joined in the celebrations as the reigning champion Chiefs returned to the Super Bowl for the fourth time in five years after upsetting the top-seeded Baltimore Ravens 17-10 in Maryland to clinch the AFC Championship crown.

The 49ers meanwhile advanced to a repeat of their 2020 Super Bowl defeat to the Chiefs after staging a stunning second-half fightback to sink the Detroit Lions 34-31.

The Lions – one of only four teams who have never played in a Super Bowl – looked poised to end that jinx after storming into a 24-7 half-time lead before a shocked 49ers home crowd in Santa Clara.

But San Francisco rattled off 27 second half points at Levi's Stadium to clinch the NFC Championship and punch their ticket to the Super Bowl, which will take place in Las Vegas on February 11.

Detroit were left ruing their risky second half decisions to pass up two kickable field goals in the second half in favor of fourth down conversions attempts that failed. On both occasions, San Francisco regained possession and marched upfield to score decisive touchdowns.

Star running back Christian McCaffrey ran in two of the 49ers four touchdowns, but was outshone by young quarterback Brock Purdy.

Purdy, finished with 267 passing yards, with one touchdown and one interception, but made a series of crucial scrambling runs at key moments to rally the 49ers.

In the AFC Championship game earlier in Baltimore, the Chiefs downed the top-seeded Ravens with a performance that melded defensive grit with clinical offense.

Ravens quarterback and presumptive MVP Lamar Jackson was stifled by Kansas City's swarming defense, while Chiefs counterpart Patrick Mahomes marshalled his team brilliantly to lead them back to the Super Bowl once more.

"It's been a heck of a year, we've been underdogs for the last few games, but we never feel like underdogs," said Mahomes, who threw one touchdown and 241 yards with no interceptions.

The Chiefs will now face the 49ers in a repeat of their 2020 Super Bowl meeting in Miami, in which Mahomes led a late rally to secure a 31-20 victory.

Another Kansas City veteran of that Super Bowl victory – tight end Travis Kelce – was outstanding in Sunday's win with 11 receptions for 116 yards, which included the Chiefs' opening touchdown.

Kelce's performance saw him burnish his Reputation as he surpassed the legendary Jerry Rice in the record books for most all-time postseason catches.