Your Ultimate Guide to UK Triathlons: July & August 2025 (Races with Open Spots!)

The sun is shining, the days are long, and the call of the open water, winding roads, and scenic run routes is getting louder. That can only mean one thing: the peak of the UK triathlon season is upon us! July and August are the golden months for multi-sport athletes, offering the perfect conditions to test your limits, smash your personal bests, and create unforgettable racing memories.

If you've been dreaming of clipping into your pedals, diving into a shimmering lake, and crossing that finish line with a triumphant roar, you're in the right place. We've scoured the country to bring you the ultimate guide to UK triathlon events in July and August 2025 that still have open registration. Whether you're a seasoned IRONMAN athlete looking for your next big challenge or a complete beginner eager to dip your toes into the world of triathlon, there's a race out there with your name on it.

So, grab your training plan, dust off your wetsuit, and get ready to be inspired. Your summer of triathlon adventure starts right here!

The UK's Summer Tri Scene: What's the Vibe in 2025?

This summer, the UK triathlon scene is buzzing with energy and opportunity. As we look at the calendar for July and August 2025, a few exciting trends emerge, painting a picture of a sport that's more accessible, diverse, and thrilling than ever.

Hotspots of Triathlon Action

If you're based in the South East or East of England, you're in for a treat! These regions are absolute hotspots for triathlon action this summer. Why? Well, it's a combination of factors. Higher population density means a bigger pool of enthusiastic triathletes like you. Plus, these areas boast some fantastic, well-established venues with excellent infrastructure. Think of the iconic Dorney Lake, the legacy of the 2012 Olympics, or the picturesque waterways of the East of England. Organisers love these locations because they offer safe, controlled environments for swimming, and flat, fast courses for cycling and running. For you, this means more choice, less travel, and a greater chance of finding the perfect race right on your doorstep.

The Big Players on the Scene

You'll notice a few names cropping up again and again in our list of events, and that's a good thing. Organisers like Active Training World (ATW) are giants in the UK triathlon world, and for good reason. Their events are known for being slick, well-organised, and consistently high-quality. When you sign up for an ATW race, you can be confident that you're in safe hands. Their repeated use of top-notch venues like Dorney Lake and Eaton Ford means they have their operations down to a fine art. For you as a racer, this means a stress-free experience where you can focus on what really matters: your performance.

More Ways to Get to the Start Line

Worried you've missed out on a spot for that super-popular race? Don't panic! Many events, like the prestigious Belvoir Castle Multisport Festival and the Outlaw Half Holkham Weekend, offer charity places as an alternative entry route. This is a fantastic way to secure your spot, especially for high-demand races that sell out quickly. Not only will you get to participate in an epic event, but you'll also be raising vital funds for a worthy cause. It's a win-win: you get to chase your athletic goals while making a real difference.

A Triathlon for Everyone

One of the most exciting trends we're seeing this year is the incredible diversity of race formats on offer. The UK triathlon scene is throwing its arms wide open to welcome athletes of all abilities and preferences. From Super Sprints for those just starting out to brutal Full Distance challenges for the ultra-endurance junkies, there's a distance for you.

But it doesn't stop there. Organisers are getting creative with formats like Aquabike (swim-bike), Duathlon (run-bike-run), and team relays. These options are brilliant for a number of reasons. If you're not a fan of open water swimming, a duathlon or a pool-based triathlon could be your perfect entry point. If you want to share the challenge with friends, a team relay is a fantastic way to experience the thrill of a multi-sport event. This inclusive approach is making triathlon more accessible than ever before, breaking down barriers and encouraging a whole new generation of athletes to give it a tri.

Your Summer 2025 UK Triathlon Calendar: Region by Region

Ready to find your next race? Here’s a detailed breakdown of the triathlon events with open registration across the UK for July and August 2025.

A. South East England: The Heart of the Action

The South East is a triathlete's paradise this summer, with a packed calendar of events at some of the UK's most iconic venues.

ATW Midweek Dorney Triathlon - July 2025

• Date: Wednesday, 2nd July 2025

• Location: Dorney, Windsor, Berkshire/Buckinghamshire border

• Distances: Super Sprint (400m swim, 10km cycle, 2.5km run), Sprint (750m swim, 20km cycle, 5km run), Sprint Aquabike (750m swim, 20km cycle)

• Why you should race: Fancy a midweek hit-out at a world-class venue? This is your chance to race on the hallowed ground of the 2012 Olympic rowing venue. The lake is calm and clear, and the bike and run courses are pancake-flat and lightning-fast. It's the perfect opportunity to chase a new PB without the weekend crowds.

• Registration: Open now, with prices from around £63.

Conquer the Chilterns Triathlon July 2025

• Date: Saturday, 12th July 2025

• Location: Henley-on-Thames, Oxfordshire

• Distances: Middle (1900m swim, 96km bike, 20km run), Standard (1500m swim, 48km bike, 10km run), Sprint (750m swim, 24km bike, 5km run), plus Aquabike options.

• Why you should race: If you like your races with a side of stunning scenery, this one's for you. You'll swim in the iconic River Thames, cycle through the rolling hills and picturesque lanes of the Chilterns, and finish with a challenging trail run through Great Wood. It's a true test of endurance with a quintessentially English backdrop.

• Registration: Open now, with prices from £66 to £108.

ATW Dorney Triathlon - July 2025

• Date: Sunday, 13th July 2025

• Location: Dorney, Windsor, Berkshire/Buckinghamshire border

• Distances: Super Sprint (400m swim, 10km cycle, 2.5km run), Sprint (750m swim, 20km cycle, 5km run), Standard (1500m swim, 40km cycle, 10km run), with relay options.

• Why you should race: Another chance to experience the magic of Dorney Lake! This weekend event is always popular, with a fantastic atmosphere and a course designed for speed. Whether you're a beginner or a seasoned pro, the clear water and flat, closed roads make this an ideal race for everyone.

• Registration: Open now, with prices starting from around £62.

The One on the River - Marlow - July 2025

• Date: Sunday, 13th July 2025

• Location: Marlow, Buckinghamshire

• Distances: A huge range of options, from 750m swims to Middle Distance triathlons (1900m swim, 91km cycle, 20km run). Aquathlons, Aquabikes, and Duathlons are also available.

• Why you should race: This is more than just a triathlon; it's a full-blown festival of endurance sports. With so many different races on offer, there's something for everyone in the family. It's the perfect opportunity to get your friends and family involved in the sport, whether they're swimming, cycling, running, or cheering you on.

• Registration: Open now, with prices from around £27.

Fareham Triathlon Series 2025

• Date: Sunday, 13th July 2025

• Location: Fareham, Hampshire

• Distances: Sprint (750m swim, 20km bike, 5km run), with individual and team options.

• Why you should race: A popular annual event that takes you through some of Hampshire's most beautiful countryside and along its stunning coastline. It's a great choice for those who want a scenic race with a friendly, welcoming atmosphere.

• Registration: Open now.

TriBourne Festival of Endurance 2025

• Date: Sunday, 20th July 2025

• Location: Eastbourne, East Sussex

• Distances: Various triathlon, aquabike, swimming, and running options.

• Why you should race: Set against the dramatic backdrop of the South Downs and the English Channel, the TriBourne Festival of Endurance is a truly spectacular event. Eastbourne is known for its challenging climbs and breathtaking views, making this a race that will test you and reward you in equal measure.

• Registration: Open now, with prices starting from around £48.

ATW Midweek Dorney Triathlon - August 2025

• Date: Wednesday, 27th August 2025

• Location: Dorney, Windsor, Berkshire/Buckinghamshire border

• Distances: Super Sprint (400m swim, 10km cycle, 2.5km run), Sprint (750m swim, 20km cycle, 5km run), Sprint Aquabike (750m swim, 20km cycle).

• Why you should race: Your last chance of the summer to race at Dorney! If you missed the July events or you're looking for one last speed session before the end of the season, this is the perfect opportunity.

• Registration: Open now, with prices from around £63.

B. East of England: Big Skies and Epic Challenges

The East of England offers a diverse range of triathlons, from full-distance epics to beginner-friendly events in beautiful rural settings.

ATW Odyssey Full Distance Triathlon 2025

• Date: Saturday, 5th July 2025

• Location: Eaton Ford, Cambridgeshire

• Distances: Full Distance (3.8km swim, 180km bike, 42.2km run)

• Why you should race: This is the big one. The ultimate test of endurance. If you've ever dreamt of becoming an IRONMAN, the Odyssey is your chance to prove you have what it takes. You'll swim in the River Ouse, cycle through the rolling countryside of Cambridgeshire, and run a marathon around the historic town of St Neots. Crossing the finish line of this race will be a moment you'll never forget.

• Registration: Open now, with prices from around £298.

Hitchin Triathlon 2025

• Date: Sunday, 6th July 2025

• Location: Hitchin, Hertfordshire

• Distances: Sprint Triathlon (likely 400m pool swim, 20km road cycle, 5km road run) and Aquabike.

• Why you should race: A fantastic event for beginners and seasoned pros alike. The pool swim is a great way to ease into the sport if you're not a fan of open water, and the course is designed to be enjoyable for all abilities.

• Registration: Open now.

Outlaw Half Holkham Weekend 2025

• Date: Sunday, 6th July 2025

• Location: Holkham Hall, Wells-next-the-Sea, Norfolk

• Distances: Half Ironman (1.2-mile swim, 56-mile bike, 13.1-mile run), plus a new Gravel Sprint on Saturday (750m swim, 19km bike, 5km run). Aquabike options are also available.

• Why you should race: The Outlaw series is legendary in the UK triathlon community, and the Holkham Hall event is one of the most beautiful. You'll swim in a serene lake, cycle through the stunning Norfolk countryside, and run in the grounds of a magnificent stately home. The atmosphere is electric, and the sense of achievement at the finish line is immense.

• Registration: Open now, with charity places available for Alzheimer's Research UK from a £50 registration fee.

Bedford Triathlon Team Relays 2025

• Date: Sunday, 20th July 2025

• Location: Box End Park, Bedford

• Distances: Team relay where each of the three athletes completes a mini-triathlon (750m swim, 20km bike, 5km run).

• Why you should race: Want to share the triathlon experience with your friends, clubmates, or colleagues? This is the perfect event for you. The team relay format is all about fun, camaraderie, and friendly competition. It's a great way to introduce new people to the sport in a supportive and exciting environment.

• Registration: Open now, with prices from around £198 per team.

The Felixstowe Triathlon 2025

• Date: Sunday, 20th July 2025

• Location: Felixstowe, Suffolk

• Distances: Super Sprint (300m pool swim, 20km cycle, 3km run), Sprint (750m sea swim, 20km cycle, 5km run), Standard (1500m sea swim, 38km cycle, 10km run), with relay and Aquabike options.

• Why you should race: A triathlon with a choice of pool or sea swim! This is a fantastic feature that makes the event accessible to a wider range of athletes. The sea swim along Felixstowe beach is a brilliant experience for those who love the open water, while the pool swim provides a great alternative for beginners. The run along the promenade is flat and fast, with plenty of support from spectators.

• Registration: Open now.

C. West Midlands: River Swims and Rural Charm

The West Midlands offers some truly unique racing experiences, with events that take you through the heart of the English countryside.

Upton Triathlon 2025

• Date: Saturday, 12th July 2025

• Location: Upton-upon-Severn, Worcestershire

• Distances: Sprint and Standard distances for Triathlon, Duathlon, Aquabike, and Aquathlon.

• Why you should race: How about a swim in the mighty River Severn? This event offers a unique open water experience, followed by a scenic bike ride and a run through the fields of Upton. It's a classic grassroots triathlon with a friendly, welcoming atmosphere. Plus, the organisers have a contingency plan in place to turn the race into a duathlon if the river is unsafe, so you can be sure your race will go ahead.

• Registration: Open now.

Shropshire Triathlon 2025

• Date: Sunday, 31st August 2025

• Location: The Mere, Ellesmere, Shropshire

• Distances: Middle (2km swim, 78km cycle, 20km run), Olympic (1.5km swim, 39km cycle, 10km run), Sprint (750m swim, 25km cycle, 5km run), with relay options.

• Why you should race: A stunning race in the heart of the Shropshire countryside. You'll swim in the beautiful Mere, cycle through rolling hills and picturesque villages, and finish with a run on fully closed roads. It's a challenging but rewarding course, and the World Qualifier medal and T-shirt for all finishers are a great touch.

• Registration: Open now, with prices from £89 to £179.

D. East Midlands: Castle Views and Countryside Cycles

The East Midlands is home to some truly spectacular events, combining tough racing with breathtaking scenery.

Belvoir Castle Multisport Festival 2025

• Date: Friday-Saturday, 18th-19th July 2025

• Location: Belvoir Castle, Leicestershire

• Distances: A huge range of options, from 'starter' triathlons to 'The Gauntlet' half-iron distance (1.9km swim, 90km cycle, 21.1km run). Duathlons, aquabikes, aquathlons, swims, and runs are also available.

• Why you should race: Race in the grounds of a fairy-tale castle! The Belvoir Castle Multisport Festival is an incredible event for the whole family. With races for all ages and abilities, it's a true celebration of multi-sport. The views from the castle are breathtaking, and the festival atmosphere is second to none.

• Registration: Open now, with charity places available for Alzheimer's Research UK from a £10 registration fee.

ATW Oundle Triathlon 2025

• Date: Sunday, 17th August 2025

• Location: Oundle, Northamptonshire

• Distances: Super Sprint, Sprint, Sprint Relay, and Sprint Aquabike, all with a pool swim.

• Why you should race: Another fantastic pool-based triathlon from ATW. If you're looking for a friendly, well-organised event to round off your summer season, the Oundle Triathlon is a great choice. The pool swim is perfect for beginners, and the bike and run courses take you through the charming Northamptonshire countryside.

• Registration: Open now, with prices from around £63.

E. South West England: City Sprints and Future Races

The South West offers a mix of urban racing and scenic countryside challenges.

ATW Bristol Triathlon 2025

• Date: Sunday, 6th July 2025

• Location: Cumberland Basin, Bristol

• Distances: Sprint (750m swim, 20km cycle, 5km run) and Standard (1500m swim, 40km cycle, 10km run), with Aquabike and relay options.

• Why you should race: A triathlon in the heart of one of the UK's most vibrant cities. You'll swim in the historic Cumberland Basin, cycle on closed roads along the Portway, and run alongside the river. It's a fast, exciting course with a brilliant atmosphere.

• Registration: Open now, with prices from £79.50 to £132.50.

SWMA Tri Series Race 4

• Date: Tuesday, 12th August 2025

• Location: Wotton-under-Edge, Gloucestershire

• Distances: Expected to be a Sprint Triathlon (0.75km swim, 18km cycle, 5km run).

• Why you should race: This one is for your diary! Registration for this popular series opens on Thursday, 24th July 2025. Set a reminder now so you don't miss out on the chance to race in this beautiful part of the Cotswolds.

F. Yorkshire and the Humber: Northern Grit and a Warm Welcome

Yorkshire offers a fantastic event at a top-class sports facility.

York Triathlon 2025

• Date: Sunday, 17th August 2025

• Location: York Sport Village, York, North Yorkshire

• Distances: Super Sprint (200m swim, 10km cycle, 2.5km run), Sprint (400m swim, 20km cycle, 5km run), and Fun categories, with a Sprint Relay option.

• Why you should race: A brilliant event for all abilities at the fantastic York Sport Village. The #TriTogether wave is perfect for those who want to experience a triathlon without the pressure of competition, and the CRUK Wave is a great way to race for a cause. It's a friendly, inclusive event with a great atmosphere.

• Registration: Open now, with prices from £79.

No Race in Your Region? Don't Despair!

If you don't see a race listed in your immediate area, don't be disheartened! Our list focuses on events with confirmed open registration for July and August 2025. There may be other events that are already full or have yet to open for registration.

Why not make a weekend of it and travel to a new part of the country for a race? A triathlon 'race-cation' is a fantastic way to explore the UK, discover new places, and meet fellow athletes. Or, you could broaden your search to include other types of events, like duathlons, aquathlons, or open water swims. The most important thing is to get out there, get active, and have fun!

Get Ready to Race!

So there you have it – your comprehensive guide to the UK triathlon scene for July and August 2025. With so many fantastic events to choose from, there's never been a better time to be a triathlete in the UK.

Now it's over to you. Which race has caught your eye? Are you taking on your first-ever triathlon or aiming for a new PB? Let us know your plans in the comments below!

And remember, the most important part of any race is to enjoy the journey. Train smart, race hard, and soak up every moment of the experience. We'll see you at the finish line!

Disclaimer: Please remember that event registration statuses can change quickly. Whilst this information is correct at the time of writing, we strongly recommend checking the official event websites for the most up-to-date information on availability, pricing, and race details before you book your place. Good luck!

Table 1: UK Triathlon Events (July & August 2025) - Overview