Penn State was not to be denied. Not this year. Not this team.

Mac O’Keefe punctuated one of the most riveting games of this college lacrosse season, scoring his sixth goal on the first possession of overtime to lift the top-ranked and top-seeded Nittany Lions to an 18-17 victory over 15th-ranked and second-seeded Johns Hopkins in the Big Ten championship game Saturday in Piscataway, N.J.

O’Keefe added two assists for a team-high eight points, while Grant Ament set the NCAA single-season record for assists. Ament’s setup of a Jack Kelly man-up goal in the third quarter was his fourth assist of the game and 78th of the season, moving him past Albany’s Lyle Thompson (2014) and UMBC’s Steve Marohl (1992) for the record.

Joey Epstein, Johns Hopkins’ sensational freshman, scored seven goals and added two assists in what was a slugfest from the outset.

The Nittany Lions jumped out to a 4-1 lead, the Blue Jays answered with five straight goals and it went back and forth from there.

Johns Hopkins nudged ahead 11-8 at halftime, the first time a Feb. 23 loss at Yale — Penn State’s lone loss this season — that the Nittany Lions have trailed at the break. The 19 goals were the most in a half in Big Ten tournament history.

Penn State came out on fire in the third quarter, scoring five goals in the first five minutes to take a 13-11 lead.

The teams went punch-for-punch from there, until Epstein landed two haymakers in the final minute. He scored twice in 11 seconds. The second tally came after Evan Zinn swooped in to scoop the ball off the faceoff, sprinted forward and spun the ball to the left alley, where Epstein caught it and buried it to tie the game at 17 with 23 seconds remaining in regulation.

Hopkins almost won it, but Nittany Lions goalie Colby Kneese held his ground on a straightaway shot by Matt Hubler with 10 seconds left. Then Penn State nearly won it after a full-field heave, but Jack Kelly stepped in the crease with four seconds left and the game went to overtime.

After Jake Glatz won the faceoff and missed on a shot, TJ Malone took his defender behind the goal, spun at the goal line and skipped a pass over the top to O’Keefe, who sent a low bouncer past goalie Ryan Darby and induced a deluge of Nittany Lions players onto the field to celebrate.

Penn State, which has never won an NCAA tournament game, clinched the Big Ten’s automatic qualifier with the win and will almost certainly be the No. 1 overall seed.

Johns Hopkins will await its fate, but the Blue Jays are on solid footing for an at-large berth thanks to two wins over Maryland in a five-day span, the second coming in Thursday’s conference semifinals.