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Flat 100K ultra runs in UK

Find flat 100k ultra runs in UK in 2025/2026 - filter by date, location or category, display on a map or use the advanced search to find your perfect race.

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  • Sun 22 Mar 2026
Sowerby Bridge, West Yorkshire, UK

Canalathon-Ultra Running Festival | 100K

  • 100 km road running + 377 m ascent
  • Fri 11 - Sun 13 Sep 2026
London, UK

Thames Path Ultra Challenge

  • 100K ultra run 2
  • 50K ultra run 2
  • Trail run 4
  • Ultra run
  • 10K run
  • + 4 more races

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