| 451 | 21 Sep 25 | 2025 Ohio Fall Challenge Triathlon . . | triathlon | New Holland, OH |
| 452 | 16 Nov 25 | 2025 Oilman Texas Triathlon | triathlon | Montgomery, TX |
| 453 | 27 Nov 25 | 2025 Oklahoma City Turkey Tracks 5K and 1-Mile Fun Run | 1M/5K/Running/1 Mile | Oklahoma City, OK |
| 454 | 13 Sep 25 | 2025 Oktoberfest 5k | 5K | Breckenridge, CO |
| 455 | 19 Sep 25 | 2025 Oktoberfest 5k/10k | 10K/5K | Alexandria, VA |
| 456 | 23 Aug 25 | 2025 Oldham County/OCPR Sprint Triathlon | triathlon | LaGrange, KY |
| 457 | 14 Sep 25 | 2025 One Last Tri | triathlon | White Bear Lake, MN |
| 458 | 16 Aug 25 | 2025 Oregon Kids Triathlon | triathlon | Oregon, WI |
| 459 | 24 Aug 25 | 2025 OTILLO SwimRun Mackinac Island | triathlon | Mackinac Island, MI |
| 460 | 27 Sep 25 | 2025 Outdoorsman Triathlon | triathlon | Bryson, NC |
| 461 | 13 Sep 25 | 2025 Outer Banks Triathlon | triathlon | Manteo, NC |
| 462 | 27 Sep 25 | 2025 Over Under Biathlon & 5K | triathlon | Surf, NC |
| 463 | 20 Sep 25 | 2025 Pacific Coast Triathlon | triathlon | Laguna Beach, CA |
| 464 | 06 Sep 25 | 2025 Palouse Sprint Triathlon/Duathlon | triathlon | Moscow, ID |
| 465 | 05 Oct 25 | 2025 Para Endurance Adaptive Triathlon . . | triathlon | Pflugerville, TX |