TALLAHASSEE, Fla. — Samantha Show retired the final 18 Florida State batters and Michaela Richbourg blasted an opposite-field, two-run home run in the top of the ninth inning Thursday night to rally Oklahoma State to a 3-1 victory over the defending national champions in Game 1 of their NCAA Super Regional.

Richbourg’s homer scored Madi Sue Montgomery, who led off the ninth with a double. It was Richbourg’s 14th homer of the season, the highest single-season total posted by a sophomore in school history.

Show (20-7) closed the door with a 1-2-3 ninth.

It was the seventh time this season that OSU came from behind to defeat a ranked opponent, and it was the Cowgirls’ highest-ranked road win since defeating No. 1 Florida 1-0 in the Gainesville Regional on May 21, 2017.

“Obviously a really good softball game,” OSU coach Kenny Gajewski said. “I didn’t like the way we started. I thought (Florida State pitcher Meghan) King was really good and had us tied up, but we adjusted and got that done.”

Game 2 of the best-of-3 series is 6 p.m. Friday (ESPN) at JoAnne Graf Field.

The Cowgirls had tied the game in the sixth when Chelsea Alexander doubled to lead off, went to third on Show’s one-out single and scored on Montgomery’s sacrifice fly to right field.

With her RBI and double, Montgomery has posted 31 homers, 51 doubles and 202 RBIs in her career. She and Oklahoma’s Sydney Romero are the only two players in Big 12 history to join the 30-50-200 club.

No. 4 seed Florida State (54-8) scored in the second on a leadoff double by Dani Morgan and singles by Anna Shelnutt and Makinzy Herzog.

After that, Show (20-7) was in control. She allowed five hits, struck out five and walked one.

“I’m really proud of Sam,” Gajewski said. “I think through two innings she gave up four hits, and then (gave up just) one the rest of the way against a really good offense and a really good team on the road. I think she got stronger as the game went.”

OSU 3, FLORIDA STate 1 (9)

OSU 000 001 002 — 3 7 1

FSU 010 000 000 — 1 5 0

Show and Thomas; King, Sandercock (9) and Shelnutt. W: Show (20-7). L: King (29-6). HR: OSU, Richbourg (14).