Thames Ring 100 Mile Ultra Marathon

Thames Ring 100 Mile Ultramarathon

Experience the magic of the legendary Thames Ring ultra on a slightly more manageable, but still brutal, scale. The Thames Ring 100 mile ultra marathon tackles the final, flat, and fiercely demanding 100 miles of Europe’s most infamous river and canal loop.

New for 2026, Challenge Running has expanded the iconic 250 mile Thames Ring into a series, offering runners the chance to take on specific sections of the route. The TR100 is a brilliant 100 mile point-to-point ultramarathon that promises beautiful scenery, logistical excellence, and the notoriously strict self-sufficiency rules that make Challenge Running events so highly respected.

Course

While the full 250-mile race starts on Wednesday, the 100 milers get to sleep in until Friday. The race begins at midday from Nether Heyford Village Hall in Northamptonshire (which serves as Checkpoint 6 for the runners doing the full 250 mile distance).

From Nether Heyford, you will head south, navigating the serene and deeply rural towpaths of the Oxford Canal before joining the River Thames path to bring you home to the finish line at the Morrell Rooms in Streatley-on-Thames.

The terrain is almost entirely flat. While this sounds appealing, 100 miles of repetitive motion on hard-packed towpaths is a serious test of muscular endurance.

To preserve the spirit of the Thames Ring, all runners must adhere to strict rules:

• No Pacers: Buddy runners and pacers are strictly forbidden. You must conquer the distance under your own steam.
• Strict Crewing: Your friends and family are actively encouraged to support you, but they may only provide assistance at designated checkpoints. Receiving outside help (food, drink, or gear) anywhere else on the course risks immediate disqualification.
• Drop Bags: Unlike the longer distances where bags go to every checkpoint, TR100 runners are permitted one 20kg drop bag which is only accessible once, at the halfway checkpoint in Lower Heyford (CP2 for this race).

Runners are supported by well-stocked checkpoints roughly every 25 miles, offering hot and cold food, hydration, and a place to briefly rest. You have a generous 34 hours to complete the 100 miles, making it an excellent option for those stepping up to the distance for the first time, provided you can manage your pace between the strict checkpoint cut-offs. For full details and registration info, please visit the official race website.