Meredith Fitzmaurice had no intention of winning the Run for Heroes Marathon this past Sunday — but she did anyway.

The long-distance runner — an elementary school teacher by trade — planned on running only half of the way as part of a training regimen for her first full marathon in Detroit, but accidentally took a wrong turn and ended up running the whole 26.2 miles.

"I just run with my watch, so I was watching my time since I planned to do my half in under 1:28," the Belle River, Ontario, native told Postmedia News. "But I'm looking at the time and wondering where the finish line is."

As it turned out, somewhere along the way Fitzmaurice inadvertently entered the full marathon course.

"Once I realized what I had done, I figured, well I'll just run 20 miles and use it as a long run and call it a day," she told the news agency.

But something tempted her to go all the way: The fact that no women were ahead of her.

"I had only ever run 20 miles, but I think at that point the adrenalin just pulled me through," the 34-year-old recalled.

High-fives from excited onlookers helped her vanquish the last couple of miles, and sail into the finish line first among female runners with a time of 3:11:48.

"If I knew I was going to be running the full marathon I probably wouldn't have ran so fast," Fitzmaurice said. "So maybe it was a good thing."

With her excellent time, Fitzmaurice should now be able to skip Detroit and go straight to the race for which she was attempting to qualify: The Boston Marathon.

[photo via Twitter]