The San Francisco 49ers overturned a 17-point half-time deficit to book a Super Bowl clash with the defending champions, the Kansas City Chiefs.

The 49ers scored 27 unanswered points as they beat the Detroit Lions 34-31 in the NFC Championship game to book a trip to Las Vegas.

It is their second Super Bowl appearance in five seasons having lost to the Chiefs four years ago.

Victory – and the chance to win a Super Bowl for the first time in 29 years – looked a long way off when Jameson Williams ended the opening drive with a 42-yard touchdown run and David Montgomery went in from close range to give the Lions a 14-0 lead in the first quarter.

Christian McCaffrey cut the gap from two yards early in the second quarter, but Jahmyr Gibbs ran in from 15 yards and Michael Badgley added a field goal to stretch the Lions’ cushion.

The game swung after the interval as the 49ers scored 17 points in eight minutes.

Jake Moody landed a field goal before Brandon Aiyuk caught a six-yard touchdown pass from Brock Purdy – after the pair had connected on a 51-yard throw via the face mask of the Lions’ Kindle Vildor – and McCaffrey went in again to level the scores.

Moody kicked them ahead for the first time before Elijah Mitchell’s three-yard run stretched the advantage, Williams’ late score leaving the Lions too little time to create another chance and ruing two failed fourth down attempts in kickable range.

“We played as bad of a first half as we could,” coach Kyle Shanahan told Fox. “It’s been a long year to get to this point and we got it done today.

“It was hard at the beginning, but the character we have in our team, the type of guys we have, we can’t wait to get to Vegas, man.”

The Chiefs will defend their Super Bowl title after beating the Baltimore Ravens 17-10 in the AFC Championship game.

Quarterback Patrick Mahomes completed his first 11 pass attempts and threw for 241 yards and a touchdown, but it was the Chiefs defence which was largely responsible for securing a fourth Super Bowl appearance in five years.

The Ravens were restricted to just 10 points on home soil and quarterback Lamar Jackson was intercepted in the end zone in the fourth quarter as he attempted to round off what would have been a 99-yard drive.

Mahomes told CBS: “God put a lot of adversity in our way this year and we accepted the challenge and we’re better for it.

“It’s been a heck of a year, we’re not done yet, but this is the way to get there.”

The Chiefs had reached the AFC Championship game for a sixth straight season, but did so by winning on the road for the first time with victory at the Buffalo Bills last week.

“We’ve been underdogs for the last few games but we never feel like underdogs,” Mahomes added.

“We’ve got a lot of guys in this team that know how to win and when the play-offs came around I knew we were going to make it happen.

“Now we’re in the Super Bowl and the job’s not done. We’ve got to go out there to Vegas and play a great team and see if we can get the Super Bowl.”

Kansas City, who will bid to become the NFL’s first back-to-back champions since the New England Patriots in the 2003 and 2004 seasons, signalled their attacking intent from the off against the Ravens, refusing to punt on fourth and two on their opening drive.

That allowed Mahomes to keep the drive alive with a 13-yard completion to Travis Kelce – who was watched from the stands once more by girlfriend Taylor Swift – and the same pair combined on a 19-yard touchdown throw to give the Chiefs an early 7-0 lead.

The Ravens responded in kind as Jackson ran for 21 yards on fourth and one from his own 34 and three plays later Jackson hit Zay Flowers from 30 yards to level the scores, only for the Chiefs to compile a 16-play, 75-yard drive capped off by a two-yard touchdown run from Isiah Pacheco.

A frenetic start also included Jackson recording a 13-yard completion to himself after reacting quickest to catch his own pass after it was tipped at the line of scrimmage, but the only other score in the first half – a 52-yard field goal from Harrison Butker – gave the Chiefs a 17-7 lead.

The contest was arguably decided on two key plays at the end of the third quarter and start of the fourth, with Flowers squandering the momentum of a 54-yard reception by taunting cornerback L’Jarius Sneed and incurring a 15-yard penalty.

Sneed had the last laugh in the first play of the fourth quarter, punching the ball loose as Flowers dived for the end zone, and when Deon Bush intercepted Jackson on the Ravens’ next drive, the game was effectively over.