Leading the way for the fifth-seeded Buckeyes was star forward Jantel Lavender, who scored a single-game tournament record 37 points while outshining MSU stars Kalisha Keane and Lykendra Johnson in front of 6,757 fans at Conseco Fieldhouse.
The Spartans (26-5) won the Big Ten's regular season crown with major contributions from Keane, the Big Ten co-Player of the Year along with Lavender, and Johnson, the conference defensive player of the year, but they never solved the Buckeyes (21-9), who beat them in all three meetings.
"I think the times we played Michigan State our team has really understood who we are as a team and really played hard and took the roles that we were supposed to play," Lavender said. "I don't think it's necessarily we get up for them, it's just that our team has kind of turned the corner from where we were in the beginning of the season."
Lavender keyed a half-ending 17-6 spurt that gave Ohio State a 43-33 lead at the end of what was a wildly competitive and entertaining first half.
The senior forward put Ohio State ahead 28-27 with a hook shot at the 6:09 mark, then teammate Samantha Prahalis stretched the lead to four with a three-pointer from the left wing.
Jasmine Thomas struck for Michigan State with a short jumper in transition, but Lavender went right back to work by swishing a 16-foot shot from the right elbow.
Cetera Washington answered with an MSU layup, then Ohio State closed things out for the half with a pair of Lavender free throws and two more by Johnson.
Johnson's trip to the charity stripe was made possible by a clutch save by Schulze, who dove at the baseline to throw a ball back into her teammate, who was fouled in the scramble by Poole with only two seconds on the clock.
Lavender finished a nearly flawless first half with 21 points on 9 for 10 shooting, leaving her 10 points ahead of Keane, who tallied 11 points on 4 for 9 shooting.
Much of Lavender's damage came against Johnson, who was left to guard her one on one.
Ohio State came out in a major funk on offense in the second half after Michigan State head coach Suzy Merchant opted to have Johnson play behind Lavender instead of fronting her, as she had in the first half.
That brought the Buckeyes' ball movement nearly to a halt as they struggled to get other people involved.
The Spartans caught the Buckeyes at 47 points, tying the game with 11:55 to go thanks to a Johnson jumper, but Ohio State's resolve would not be broken.
Lavender snapped a 51-all tie when she made a 15-foot shot at the 8:23 mark, beginning a 13-0 run that put the regular season champions on ice.
Johnson picked up her fourth foul when trying to go over Lavender's back for a free throw, and the Buckeye senior made both ends of a one-and-one to extend the lead to four.
Much to Merchant's chagrin, her team turned the ball over on its next three possessions, miscues that led to seven more Ohio State points in a row and suddenly had the Buckeyes leading by nine with 6:37 left.
"Our focus was a little off track, but we quickly got it back," Ohio State head coach Jim Foster said. "In tournament play, the games are officiated differently. What was a foul last night wasn't a foul tonight. You have to adjust and figure it out and get out there and really get after it."
Their advantage reached 13 after a layup and two more Lavender free throws, and the Spartans never recovered.
Ohio State ended up 22 for 26 from the free throw line while MSU was 8 for 12. That 14-point disparity helped offset a 19-6 Michigan State advantage in second-chance points.
"Coach Foster always says one way of showing toughness is getting to the free throw line and knocking down free throws," said OSU guard Tayler Hill, who was 5 for 7 from the charity stripe and scored nine points with five assists. "I think we just kept attacking and we made the ref blow the whistle the way we were attacking."
Keane finished with 17 points to lead the Spartans, who also got 14 from Johnson and 10 from Poole.
The Buckeyes will face No. 2 seed Penn State in the championship game at 3:30 p.m. on Sunday afternoon.
The two teams split the season series with the home team winning both games.