Gatlin's pinch single into short right field over a pulled-in, five-man infield in the bottom of the ninth inning gave the Rebels a 2-1 victory over Texas Tech in an elimination game.
The exciting finish came after Texas Tech had tied it in the top of the ninth on a couple daring steals and a sacrifice fly.
"When the game is on the line like that, we're each called upon in different situations and every one of us feels prepared for it and expects to get the job done," Gatlin said. "That just goes back to the toughness we've been preaching all year."
Ole Miss (47-20) plays TCU on Thursday in another elimination game.
"In this ballpark everything just seems amplified — every pitch, every error, every walk, every base hit. You can feel it in this stadium because runs are such a premium here. To pull one out, to get the win column here in Omaha for the first time since 1969 is huge."
The Red Raiders (45-20) went 0-2 in their first CWS.
"We line up to play and we want to win," Tech coach Tim Tadlock said, "so right now it's kind of an unusual feeling for me because we did do something these guys will hold forever. At the same time, we're going to lay our head down every night and wake up every morning trying to get back."
Ole Miss won after Colby Bortles walked with one out. Brantley Bell hit a comebacker to Cameron Smith, who tried to force out Bortles at second. But he threw high into center field, allowing Bortles to go to third.
Aaron Greenwood then pinch ran for Bortles, Dominic Moreno came on to face Gatlin and Texas Tech shifted an extra player to the left side of the infield and went with only two outfielders. Gatlin punched a 1-2 pitch over second base, Greenwood scored, and the celebration was on.
"We've done that throughout the entire season where (players) 1 through 27 contribute in some form or fashion," Gatlin said.
Scott Weathersby (4-4) got the win for an inning of relief of left-hander Christian Trent, who allowed six hits, walked one and struck out six in eight innings.
Smith (8-3) took the loss after working a third of an inning. Tech freshman starter Ryan Moseley had pitched 7 1-3 strong innings.
Tech tied it 1-1 in the top of the ninth. Adam Kirsch singled with one out, and Zach Davis entered as a pinch runner. With pinch hitter Anthony Lyons at the plate, Davis stole second and third. Lyons then lofted a sacrifice fly to right to bring in Davis.
Ole Miss broke a scoreless tie in the seventh in what, up to then, had been another frustrating offensive day. The Rebels had entered the CWS with a .303 batting average that was best among the eight teams in Omaha. But they managed only one hit in their 2-1 loss to Virginia on Sunday and were 4 for 49 (.082) in the CWS when Holt Perdzock stepped in against Ryan Moseley.
Perdzock sent Moseley's first pitch down the third-base line, allowing Sikes Orvis to score from second.
Ole Miss is 13-9 in one-run games this season, including 2-1 in the NCAA tournament.
Texas Tech was 1 for 14 with runners in scoring position in two CWS games, including 0 for 6 on Tuesday.
"It's why we keep showing up, because it's very unpredictable — just an inch here or an inch there, and the game could go either way," Tadlock said. "At the same time, Ole Miss earned it. They earned the right to move on, and good luck to them."