OKLAHOMA CITY (AP) -- Shay Knighten didn't let Oklahoma waste any more opportunities.
Her three-run homer off Kelly Barnhill in the top of the 17th inning gave the Sooners a 7-5 victory over Florida in Game 1 of the championship series on Monday night.
Oklahoma left the bases loaded in the 15th and 16th innings before Knighten put the Sooners in control.
"I was just looking to find a pitch in the zone that I could hit hard," she said. "I wasn't looking for really a particular pitch. It was just something -- I knew she was throwing hard, so it's just get there, just get there, and if it was in the zone, I was going to swing."
The matchup between programs that have split the past four national titles was the longest championship series game in NCAA history. It lasted 5 1/2 hours, and all four pitchers threw more than 100 pitches.
"Epic, epic battle," Oklahoma coach Patty Gasso said. "I don't know what else -- that was it. This is one of the greatest games I think in College World Series history, I would guess. It was like two heavyweight fighters throwing punch after punch. Florida just kept answering everything that we put out there, and we tried to answer back, and it was a game of will, a game of team, a game of character."
Florida coach Tim Walton said he was impressed with his team's resilience. The Gators extended the game twice after being down to their last strike.
"I told my team in about the -- I don't know if it was the eighth or the 21st, whatever inning it was, I told them great job, proud of you guys," he said.
Oklahoma (60-9) can clinch a repeat championship Tuesday in Game 2 of the best-of-three series. The Sooners won national titles in 2013 and 2016. Florida won in 2014 and 2015.
Oklahoma's Paige Lowary (16-3) got the start, was replaced, then re-entered to claim the win.
Paige Parker was the most outstanding player of the series last year and had won all eight of her World Series decisions, so it was a bit of a surprise that Lowary got the start. Parker pitched 6 2/3 innings of relief.
"It was a team decision," Gasso said. "It was a pitching staff, coaching staff decision. These two were right with us when we talked about it, and then we presented it to the team and they were all for it."
Barnhill (26-4), USA Softball's National Collegiate Player of the Year, took the loss for Florida (58-9). She pitched nine innings and struck out 13. Delanie Gourley struck out 13 in eight innings of relief.
The Sooners scored the first earned runs top-seeded Florida has allowed in four World Series games.
With Oklahoma up 2-1 and two outs and two strikes against Florida's Sophia Reynoso in the bottom of the seventh, Reynoso popped the ball up. It dropped, and Alesia Ocasio scored from first to tie the game and force extra innings.
Knighten doubled off Gourley in the 12th with no outs, and Fale Aviu followed with a two-run homer to put the Sooners up 4-2, setting up Florida's second escape act.
After Lowary re-entered the game with two outs in the 12th, Amanda Lorenz, down to her last strike, knocked in two runs to tie the score at 4.
Lowary, a transfer from Missouri, settled down and gave up just one more run.
"It was highs and lows, and for Paige Lowary especially to finish on the note that she did, it was to me the highlight of our season," Gasso said.
The game severely worked the pitching staffs for both teams, but Florida's Ocasio and Oklahoma's Mariah Lopez have had strong seasons as No. 3 pitchers.
The Gators still feel they are in a good position.
"Tomorrow is a new day, and we're still in the national championship," Lorenz said. "We have two more games left, and I'm really proud to see what we have tomorrow because obviously we showed the softball world a really good game tonight, and we're not done yet."