Brock Purdy threw for 267 yards and a touchdown, and the San Francisco 49ers rallied from 17 points down at halftime to beat the Detroit Lions 34-31 on Sunday and reach the Super Bowl.

The 49ers (14-5) scored 17 points in an eight-minute span of the third quarter to tie the NFC championship game and then pulled away in the fourth quarter to earn a rematch against Kansas City after losing to the Chiefs in the Super Bowl four years ago.

San Francisco mounted the fourth comeback ever from 17 points down or more in a conference title game thanks to some big plays by Purdy and bad mistakes from the Lions (14-6), including two failed fourth downs in field-goal range. Detroit fell short of reaching the first Super Bowl in franchise history.

After being questioned about whether he could lead a comeback, Purdy has now done it twice in as many weeks. He engineered a game-winning drive in the fourth quarter to beat Green Bay last week and then had an even bigger comeback against the Lions.

Christian McCaffrey had two TD runs and little-used backup Elijah Mitchell scored on a 3-yard run to make it 34-24 with 3:02 to play as the Niners got over the conference title game hump after losing the past two seasons.