Daniel Murray, who hadn't made a field goal since the season opener, hit a 31-yarder with a second left and the Hawkeyes rallied to stun the third-ranked Nittany Lions 24-23.
All that talk about an unbeaten Penn State possibly being left out of the BCS national title game turned out to be premature. A third championship for the 81-year-old Paterno, who's had four unbeaten teams not win titles, is a long shot now.
Shonn Greene rushed for 117 yards and two touchdowns, and Ricky Stanzi bounced back from an interception and a fumble to lead the Hawkeyes (6-4, 3-3 Big Ten) on their game-winning drive, which came after Daryll Clark threw just his third interception of the season.
Murray had lost the regular field-goal duties to freshman Trent Mossbrucker and was relegated to kickoffs. But with the winds swirling and strong, coach Kirk Ferentz opted for experience and Murray's strong leg.
He drilled it down the middle, sending Iowa's freezing fans spilling onto the field.
"I've always dreamed about it," said Murray, who grew up in Iowa City. "I kept hoping and hoping I'd get my chance."
The Nittany Lions were third behind Alabama and Texas Tech in the last Bowl Championship Series standings. They'll drop Sunday. The Big Ten title and a Rose Bowl berth are the Nittany Lions' main goals now.
"We need to keep our heads up. We can still have a heck of a year," said Paterno, who again coached from the press box and got around with a cane because of a sore leg and hip.
Iowa was down 23-14 heading into the fourth quarter. But Greene scored his second TD, from 6 yards out, to make it 23-21 with 9:20 left.
On the next possession, Penn State looked as if it got a break, when Iowa was called for a roughing the punter penalty that had the Hawkeyes seething. The Nittany Lions kept the ball and continued its time-consuming march.
But Clark made an errant throw down the middle that was picked off by Tyler Sash, who returned to Iowa's 29 with 3:46 left. Iowa then caught another break when Penn State was flagged for pass interference on third down, getting the Hawkeyes near midfield with a first down.
Stanzi, who was 15-of-25 passing for 171 yards, hit Derrell Johnson-Koulianos at the Penn State 15 with 18 seconds left to set up Murray's kick.
"I want to apologize to the whole Penn State nation for my game play today," Clark said. "I just keep having that turnover recurring in my head over and over. I can't get it out of my mind."
This was the biggest win for Iowa in years, its first against a top-five team since 1990. The Hawkeyes suffered through two seasons of mediocrity after finishing No. 8 in the country three years in a row.
The Hawkeyes had lost four games this season by a total of 12 points - and they got beat last week by Illinois on a 46-yard field goal with 24 seconds left.
"We knew we had enough to win," Iowa linebacker A.J. Edds. "But there weren't a whole lot of people on the outside that thought we were the kind of team we know we are. We showed that today."
Clark was 9-of-23 for 86 yards and Derrick Williams and Evan Royster each ran for touchdowns to lead Penn State (9-1, 5-1), which had to settle for Kevin Kelly's field goals on three different trips inside Iowa's 20.
On a day where the wind chill dipped into the 20s, Penn State held the ball for nearly 36 minutes and ran almost twice as much as they threw it.
It worked for the first three quarters.
Penn State's Tyrell Sales picked off Stanzi on the opening drive of the third quarter, and Kelly's 25-yard field goal put the Nittany Lions ahead 16-7.
Iowa's offense finally woke up, reeling off a 73-yard drive that Stanzi capped by finding a wide-open Johnson-Koulianos for a 27-yard touchdown pass to pull the Hawkeyes within 16-14 with 4:43 left in the third.
But Stanzi fumbled away the ball and Iowa's momentum just two minutes later, giving Penn State the ball deep in Iowa territory after botching the snap. The Nittany Lions wasted little time turning Stanzi's mistake into points, as Williams' 9-yard touchdown run put Penn State back up 23-14 heading into the fourth. Penn State held the ball for an astounding 23:34 and outgained Iowa 203-70 in the first half. But the Hawkeyes forced a pair of red-zone field goals, keeping Penn State's lead at 13-7.
After falling behind 7-0 early in the first quarter, the Nittany Lions put together scoring drives of 71, 75 and 78 yards - all powered by the running game. They had to settle for 24-yard field goal by Kelly on the first one, but Royster ran for a 2-yard score to give Penn State a 10-7 lead early in the second quarter.
Kelly drilled a 31-yarder into the with 55 seconds left in the first half.
Iowa forced Clark to fumble on the game's opening drive, but the officials said he got it back it at the Penn State 1. The Hawkeyes thought they had recovered the ball in the end zone, but they had to settle for a Nittany Lions punt and a short field.
Greene - with Iowa's student section decked out in green shirts in honor of the nation's third-leading rusher - made Penn State pay just two plays later, scoring on a 14-yard touchdown run that put Iowa ahead 7-0.
The Nittany Lions were shooting for their first 10-0 start since 1994 - incidentally, the last time Penn State went undefeated but didn't win it all - but with home games against Indiana and Michigan State left, a Big Ten title is still Penn State's to lose.
"Their balloon still isn't busted," Paterno said. "If we win the next two we'll have an opportunity to go to a big bowl."