Marathon
- County:
- Monroe County
- County Seat:
- No
- Area (mi²):
- 8.446
- State:
- Florida
Marathon is a city located in Monroe County, Florida. Marathon has a 2026 population of 10,039. Marathon is currently growing at a rate of 1.01% annually and its population has increased by 1.85% since the most recent census, which recorded a population of 9,857 in 2020.