They finished with 286 yards as Raheem Mostert had a team-record 220 and scored four touchdowns. Roethlisberger was 9 for 21 for 123 yards with no touchdowns and two interceptions, finishing with a 22.6 passer rating (the lowest rating for a winning quarterback in Super Bowl history). Mahomes - who'll be 24 years, 138 days on January 2 - will become the fifth youngest quarterback to start a Super Bowl; it's another big accomplishment for the 2018 NFL MVP, who has played just two full seasons in the league.
The reigning NFL MVP threw for three touchdowns and danced into the end zone for a superb individual score as the Chiefs successfully neutralised the threat posed by Titans running back Derrick Henry.
But the Chiefs, as they had in overcoming the Houston Texans' 24-0 advantage last weekend, rallied behind their super quarterback.
The 49ers are going back to the Super Bowl for the seventh time in the franchise's history.
For the second time this season, the Niners dope-slapped the Packers, following a 37-8 regular-season blasting with a 37-20 win Sunday (box) that was over before the late-arriving San Francisco fans had a chance to leave early.
"If you don't have the ticket to the game, this is your Super Bowl", NFL director of events Nicki Ewell said.
This year's total of Penn Staters in the big game is the highest since Super Bowl XXXV, which was played in 2001 between the Baltimore Ravens and New York Giants. The departure of coach Jim Harbaugh and Kaepernick's kneeling saga ushered in a period of instability.
The 49ers were considered middle-of-the-pack contenders to start the season, with 40-1 Super Bowl odds at Caesars Sportsbook. Mostert's yardage total was the second-most in an National Football League playoff game behind Eric Dickerson's 248 yards in 1985.
In two weeks in Miami, they will play the victor of the NFC title game between Green Bay and San Francisco.
San Francisco had 42 runs to just eight passes on the day.