An undrafted free agent playing just his sixth postseason game, Gaudreau scored the go-ahead goal 3:45 into the second period and Pekka Rinne made 23 often-spectacular saves as the Predators beat the Penguins 4-1 on Monday night to even the series at 2-2.
It's now a best-of-three sprint to the Stanley Cup, and Nashville is riding a wave of momentum after outscoring the defending champions 9-2 in the Games 3 and 4 of their Final debut.
Gaudreau, a 24-year-old rookie, only has a chair in the Predators' locker room, but he now is the second player in NHL history to score his first three career goals in a Stanley Cup Final, joining Johnny Harms with the 1944 Blackhawks. Calle Jarnkrok, Viktor Arvidsson and Filip Forsberg also scored for Nashville, which improved to 9-1 at home.
"We were in a tough hole against a really good team, came home and took care of the home games with the help of all our great fans," Rinne said. "It's a great feeling. We played two really good games."
Sidney Crosby scored his first goal in the series after not getting a shot on goal in Game 3. The goal was his first in the Stanley Cup Final since June 4, 2009 — a span of 12 games. The goal came after he was held without a shot for only the fifth time in his career in the playoffs.
The Penguins now have lost two straight for the second time this postseason. They also lost Games 5 and 6 against Washington. Goalie Matt Murray lost consecutive games for the first time in his young career.
Game 5 is Thursday night in Pittsburgh.
Nashville tapped country singer Dierks Bentley as the latest to sing the national anthem, while country singer Jason Aldean waved the towel to rev up the crowd. Former NBA star and TV commentator Charles Barkley also was on hand, accepting NHL Commissioner Gary Bettman's invitation to watch in person.
Rain most of Monday kept the crowd outside from reaching the more than 50,000 who turned Saturday night for the first Stanley Cup Final game in Tennessee. Enough people turned out to fill up Broadway for three blocks with three giant TV screens, even with Nashville opening up a downtown amphitheater for fans to watch.
After the anthem, two catfish and one stuffed penguin hit the ice despite Nashville coach Peter Laviolette's video plea earlier Monday asking fans not to throw anything.
Craig Smith, who had two of Nashville's first six shots, ricocheted a puck off Murray's pads that Jarnkrok tapped in at 14:51 to start the fans yelling. Pittsburgh lost a challenge for goalie interference.
Then Crosby, held without a shot for only the fifth time in the postseason in his career, tied it up for Pittsburgh on a breakaway. He skated in on Rinne, holding the puck before scoring behind the goalie's leg just 66 seconds later for his eighth goal and 24th point of the playoffs.
Rinne kept it tied in the early minutes of the second first with a stop of Jake Guentzel before a big save on Chris Kunitz on a breakaway.
Play was underway when the horn sounded, and officials reviewed a play and ruled Gaudreau's wraparound attempt slid the puck just over the line before Murray stopped it. Referee Dan O'Halloran announced it as a goal, giving Nashville a 2-1 lead 3:45 into the second.
"I heard it on the bench that it was possibly in the net," Gaudreau said. "I wasn't certain. When I heard the horn, I sort of thought it was in."
Crosby had another breakaway nearly midway through the period, and Rinne stopped him not once, but twice. Then the goalie slid to his right stopping Guentzel with an assist from Nashville defenseman Roman Josi.
Arvidsson made it a 3-1 Nashville lead with his first goal since the end of the first round. James Neal started the play, getting the puck to captain Mike Fisher who fed the puck up to Arvidsson while falling to the ice. Arvidsson beat Murray under his glove, putting the puck just inside the right post at 13:08.
Forsberg sealed the win with an empty-netter with 3:23 left.
Notes: Fisher, scoreless until the Final, now has four points. He got his fourth on his 37th birthday. ... With his goal, Crosby now has 161 career playoff points and moved past Mike Bossy, Gordie Howe, Al MacInnis and Bobby Smith for 20th all-time by himself. ... The Penguins now are 13-3 after a playoff loss under coach Mike Sullivan, and Murray is 7-1 in playoff games started after a loss.