Chief's quarterback Patrick Mahomes found Mecole Hardman in the end zone deep into overtime to seal a dramatic 25-22 win in what was also the longest Super Bowl game in history.
The victory makes Kansas City the first team to win back-to-back Lombardi Trophies since the New England Patriots in 2003/2004, cementing the franchise's right to be regarded as the NFL's newest dynasty.
CBS parent company Paramount said in a statement that a total audience of 123.4 million across all platforms made it the "most-watched telecast in history" - up seven per cent from last year's game.
Paramount said 120 million people watched the NFL championship game on CBS alone, a record for a single US network.
Viewership was boosted by a confluence of non-sporting star power, with Usher leading an all-star cast that included Ludacris, Alicia Keys and Jermaine Dupri for the half-time show.
Slow jam king Usher held his own as he captured the magic of his late-1990s, early-aughts fame with a 13-minute, career-spanning medley including hits like "Love In This Club" and "OMG."
But pop superstar Taylor Swift didn't sing a word and was still the night's most-watched fan as she cheered on her boyfriend, Chiefs tight end Travis Kelce, from a luxury box with a coterie of famous friends including the rapper Ice Spice.
Swift's relationship with charismatic star Kelce has been a boon to television ratings, her every move offering headline fodder.
The "You Belong With Me" and "Anti Hero" singer's attendance at Chief's games has attracted many of Swift's younger, largely female fans - helping widen NFL viewership to a new demographic.
Beyonce was also in the stadium Sunday with her hip-hop mogul husband Jay-Z - and announced a new album during a commercial she did with telecoms giant Verizon, in which she repeatedly tries to "break the internet."
