Zach Bitter is an American ultramarathon runner. He holds world records for the 100-mile run (track) and the 12-hour run (track). Bitter claimed both records with his performance during the Six Days in the Dome event in Milwaukee, Wisconsin, on August 24, 2019. His 100-mile time of 11 hours, 19 minutes and 13 seconds, bested Oleg Kharitonov’s 2002 world record by almost 11 minutes, and was more than 20 minutes faster than his own American mark of 11:40:55. After claiming the 100-mile record, Bitter continued running for another 40 minutes and upped his own 12-hour distance world record to 104.8 miles, an improvement of more than three miles over the previous mark.
"At UW-SP, I learned that I seemed to get better as the distances got longer, so to me, ultra-running was a logic sport," said Bitter.
- Andrew Dawson (2019-08-26). "American Zach Bitter Crushes 100-Mile World Record With 6:48-Mile Pace". Runner's World. Retrieved 2019-08-28.
- Boren, Cindy (August 28, 2019). "American Zach Bitter crushed the 100-mile world record — by running 363 times around a track". The Washington Post. Retrieved August 28, 2019.
- "Zach Bitter runs 100-mile world record in 11 hours, 19 min". SI.com. Retrieved 2019-08-28.
- "Zach Bitter - Men's Track & Field". University of Wisconsin - Stevens Point Athletics. Retrieved 2019-08-28.
- "Runner Files: Zach Bitter". Orange Mud, LLC. Retrieved 2019-08-28.