Milwaukee Brewers starting pitcher Jacob Misiorowski threw the fastest recorded pitch in World Series history as his side began the best-of-seven season finale with a win.
The right-hander played a starring role in the 3-2 win at home to the Tampa Bay Rays, in the first match of the 122nd World Series.
It is only the second time in more than a century that neither side contesting the World Series has won the title before.
A sell-out crowd watched the Brewers in only their second appearance in the finale of the Major League Baseball season, and their first since losing to the St Louis Cardinals in 1982.
Milwaukee's American Family Field has 41,900 seats but with standing-room-only tickets available for the 'Fall Classic', 43,250 fans packed in to see the game.
"It was amazing - just to have the city behind me, it means the world, we couldn't ask for anything better," said Misiorowski.
The Brewers host the second match of the best-of-seven series on Saturday before the teams move to Florida for three games, then return to Milwaukee for the final two matches, if needed.
Misiorowski, 24, became the youngest starter since 1997 to win a World Series opener, after restricting the Rays to just one run in five innings.
His fastest pitch at 103.5 mph beat the previous mark of 103.2 mph set by Aroldis Chapman of the Chicago Cubs in 2016 - though speeds have only been recorded since 2008.
Brewers designated hitter Christian Yelich also played a key role, scoring one run and driving in another as they took a 3-1 lead.
The Rays added one run in the final inning and had a runner on third base as they pushed to level the score, but Milwaukee closed out victory.
"It feels great. The guys settled in right away and did a great job," Yelich said. "We've still got a ways to go but nice to get that first one."
The Brewers made the World Series by beating the Los Angeles Dodgers 4-0 to claim the National League title, while the Rays clinched the American League pennant with a 4-2 win over the Cleveland Guardians to reach the post-season finale for only the third time.
The Rays lost to the Philadelphia Phillies in the 2008 World Series and the Dodgers in 2020, but manager Kevin Cash took solace from the fact that they tested the Brewers on Friday.
"We came up a little bit short, but there's some benefit maybe from a loss," said Cash.