In what appears to be her first attempt at the 100-mile distance, Ireland’s Caitriona Jennings set a new women’s 100-mile world record at the 2025 Tunnel Hill 100 Mile with a time of 12:37:04. She eclipsed the previous record of 12:42:40, which was set by Camille Herron at the same event in 2017.
Caitriona Jennings looking pleased with her new women’s 100-mile world record. Photo: Micki Colson/Colson Photography
Jennings ran an impressively evenly split race, averaging 7:34 minutes per mile (4:42 minutes per kilometer) for the full 100-mile distance (160.9 kilometers). While temperatures were cool at the 7 a.m. CST start on November 8, things got warm throughout the middle of the day, but this didn’t seem to slow Jennings at all.
While the 100-mile distance may be a step up for Jennings, she’s no stranger to ultra distances. She set the current Irish 50k record in February 2025 at the Donadea 50k when she ran 3:16:33. The event served as the Irish 50k National Championships. She also holds the Irish 100k national record with a time of 7:43:01, set in 2021. In 2022, she won the International Association of Ultrarunners (IAU) 50k European Championships, and she’s finished in the top 10 of the Comrades Marathon at least four times.
What is perhaps the most impressive about Jennings’s 100-mile run was her consistency. For nearly the first 80 miles, her pace never wavered more than a second or two away from 7:26-minute miles. And after 80 miles, or about 10 hours of racing, her pace only slightly crept up. For the entire race, she was able to keep her pace below that of the world record.
Caitriona Jennings stops her watch with a new women’s 100-mile world record. Photo: Micki Colson/Colson Photography
The 100-mile race is held in conjunction with the Tunnel Hill 50 Mile. Earlier in the day, American Anne Flower set a new women’s 50-mile world record in 5:18:57. The course is held on the Tunnel Hill State Trail, which is a rails-to-trails gravel path with a crushed gravel surface. The most well-known landmark on the course is an old rail tunnel that runners pass through. The race consists of a flat double out-and-back starting in Vienna, Illinois, and the 100-mile racers complete both out-and-back legs twice. The course has garnered a reputation for speed, and several world records have been set here in the 50- and 100-mile distance in recent years. The course is USA Track and Field-certified, and the record will need to be ratified by the IAU.
