Paula Keating broke the three-hour mark to set a course record for women at the Fredericton Marathon Sunday.
Chuck Dixon of Sackville, N.B., crossed the line first overall.
Hundreds of runners are on the streets for the city's 36th marathon.
The first 5K runners crossed the line around 8:30 a.m., with the lead runner completing the course in under 17 minutes.
"Organizers say it's a fast, flat course. It's sunny and a great day for racing," said the CBC's Bridget Yard.
The stands are packed with spectators, many eager to see Keating's bid to break the three-hour mark in the Scotiabank Fredericton Marathon.
The Miramichi resident is the only New Brunswick woman to run a marathon in under three hours and has now done it eight times (including at the New York Marathon).
This year's course is tapping into the city's trail system and highlighting residential architecture.
"The route change allows Fredericton to become one of the many cities who have embraced the marathon as a key event to showcase their city to a large number of people," said race director Paul Lavoie.
"Our race committee hated to turn runners away last year because of the congestion on the 2013 route and we hope the route change for 2014 makes the run more enjoyable for everyone."