The best 2025 triathlon races to enter now

Major new races and familiar classics will combine in 2025 to create an unforgettable triathlon season. Here are some of the best 2025 triathlon races to enter now.

Castle Race Series: Belvoir Castle

• Location: Belvoir Castle, Leicestershire
• Distances: Multiple
• Date: 19-20 July 2025

The Castle Race Series will host its second running of the Belvoir Castle Triathlon and Multisport Festival in July on the Leicestershire estate. Over to Fran Watson of the CRS team…

“Arrive 75 minutes before your start time. Bikes can be racked in the transition area an hour before the race begins. Saturday features the shorter adult races, while Sunday hosts longer events, duathlons, an aquabike, aquathlons, and the Run Series. Junior races run each afternoon.

“With a lapped course that keeps swimmers close to the banks, the swim is ideal for newcomers to open-water swimming. The 45km bike course has 287m of elevation gain and takes in a stiff climb to the Belvoir Edge and combines wide, well-maintained country roads into a fast-paced yet challenging course.

“The 10.5 km run includes 187m of elevation, with a steep climb up Blackberry Hill and a technical descent into Frog Hollow. Trail shoes are recommended due to the varied terrain.”

If you’re looking for a training plan for this or any of the races in this guide, then head over to our training hub to find free training plans for all abilities and distances.

XTRI: The Restless

• Location: Arrochar Alps, Scotland
• Distance: 1.8km swim/50km gravel ride/25km trail run
• Date: 23 August 2025

New from the Xtri organisers of Celtman and Norseman fame comes The Restless, a unique gravel triathlon set in the Arrochar Alps north-west of Glasgow. Here’s Triathlonworkx coach Alan Cardwell on what you can expect in the Grampian Mountains come August…

“Even in August, the water temperature in the deep Loch Goil will still be chilly and, at the Carrick Castle end, it opens up to sea-like conditions. Acclimatise in cold water and experience swimming in choppy conditions ahead of the race.

“The 50km bike course is designed specifically for gravel bikes and is, in the main, fast and flowing. It is super hilly, though, so make sure your training includes steep inclines and that your legs are strong enough for the nearly 2,000m of elevation gain. There’s a section of rocky and steep singletrack that only a few athletes will manage to ride. So, practice your mounts, dismounts and some cyclo-cross-style carries before the race. 

“The run, with 1,200m of ascent over the 25km, is a classic Scottish hill run that goes relentlessly uphill to the peak of Ben Donich. The key thing, however, is the descent on tired legs, so practice your downhill skills as these will not only save you time, but keep you safe.”

Find plenty of off-road training tips throughout this website to help you, as well as the beginners’ guide to off-road biking.

Slateman Ultra

• Location: Llanberis, Eryri (Snowdonia)
• Distance: 3.8km swim/180km bike/44.5 or 49.9km trail run
• Date: 8 June 2025

One of the big new race launches of 2025 is the Slateman Ultra. The race is like a mashup of the existing, shorter Slateman events on the same day and the late Brutal events, with the run leg of the longest option venturing up to the summit of Yr Wyddfa (Snowdon) before a leg-shaking descent back to the lakeside finish line. Over to race director Brian Corcoran for their Ultra tips…

“Try to maintain your cold-water acclimatisation throughout the winter. Occasional short cold water dips are worth their weight on gold when you get to open-water swim season. When you start your specificity block of training, think about incorporating very hilly sections into your brick runs. The quarry lap and Llanberis Path both have sections where a fast power walk is the optimal strategy. Speed agility quickness training will help develop the cadence required for an efficient power walk.

“Get your race day nutrition dialled in. It’s going to be a long day and gels alone aren’t going to cut it. Try ‘real’ food as much as possible and stay away from sweet foodstuffs for as long as possible. Peanut butter sandwiches, (veggie or otherwise) sausage rolls, dried fruit and nuts, falafel and hummus… are all great options that you’ll look forward to eating. 

“Off-road trail shoes are a must. The run’s quarry section is a combination of hard-packed stony trails with muddy sections. A good all-round shoe with a rock plate and good ankle support is required. You can use lightweight running/hiking poles, too.

The weather both in Llanberis and on the summit can be wildly different. Make sure that you consider the ‘feels like’ temperature. Putting a dry layer on your top half before you start the mountain lap will help you regulate your body temperature.

“Take a trip to North Wales to familiarise yourself with the bike course, the quarry run section and the Llanberis Path. It’ll be a good chance to know what to expect and experiment with hiking poles, your nutrition, bike set up, shoe choices and more.”

If it’s the mental side that is worrying you, then check out this feature on developing mental resistance for ultra racing.

Ironman Leeds

• Location: Leeds, Yorkshire
• Distance: 3.8km swim/180km bike/42.2km run
• Date: 27 July 2025

The big new M-Dot launch in 2025 is Ironman Leeds in Yorkshire in July. Here’s Race Director for IRONMAN Leeds, Lewis Peacock, on how to prep for the debut Ironman in God’s Own Country…

“The key to making the most out of your Ironman Leeds weekend is to plan ahead, allow your focus to be on the race by knowing where you need to be and at what time. As an athlete you will need to attend registration on either the Friday or the Saturday as bike and transition bags can be racked on the Saturday only.

“There’s a lot to think about for race day. Have a race plan prepared and a specific nutrition plan in place that you’re confident will provide you with the correct amount of energy to get you through your day. Keep an eye on the weekly weather forecast and plan accordingly – make use of your blue, red and on-course personal needs bags to add any extra clothing, nutrition and equipment. Transition will open 90mins before race start.

“Kicking off your Leeds journey will be a self-seeded rolling start into the calm waters of Waterloo Lake in Roundhay Park. Keep calm, find your rhythm and control your breathing especially for the first few hundred metres. The full bike course will be released shortly, but anyone who has cycled in and around the area before will know to expect spectacular scenery and fantastic riding (top tip: hilly training rides are advised!).

“The run course will be disclosed shortly but know that has a bit of everything. It’ll be a spectator’s dream, offering your friends and family multiple locations to see you before concluding your run on the iconic red carpet of the inaugural Ironman Leeds.”

Croyde Ocean Triathlon

• Location: Putsborough, Devon
• Distance: 1.5km sea swim/37km bike ride/12km trail run
• Date: 6 July 2025

Here’s race director Jo Hibberd on how to navigate the challenges posed by this epic Olympic-distance race on the stunning North Devon coast.

“The Croyde Ocean Triathlon starts with a swim in the Atlantic at Putsborough Sands. Get in the ocean or at least open water as soon as the water is warm enough.

Here’s a free eight-week open water swimming training plan which will help.

Sighting can be a challenge if conditions are bumpy so nailing your technique can make a huge difference. As for the mass swim start, take your time and let the big guns sprint it out. Post-swim you’ll have to tackle a steep climb to the grassy transition zone. Walk it to save your legs! Many opt to leave beach shoes at the bottom of the hill.

“The bike route is hilly and technical. The winding Devon lanes, high hedges and tight turns mean you must concentrate every second of the ride. Look out for the ford at the start.

“On the trail run the climbs are steep in places. The hardest climb is around 2km into the run – many decide to power-walk here. There’s also the Croyde beach section. Most of the sand is hard but there’s a soft and energy-sapping section at the end. Take the shortest route on the soft sand and ignore the more direct diagonal route.”

Challenge Kaiserwinkl-Walchsee

• Location: Walchsee, Austria
• Distance: 1.9km swim/90km bike/21.1km run
• Date: 29 June 2025

This established event in Austria is one of the major draws on the Challenge Family calendar thanks to the superlative scenery, slick organisation and array of pre- and post-race activities. Here are Victoria Murray-Orr’s event tips…

“As Walchsee is 660m above sea level the weather can be changeable – hot and sunny one day and cold and wet the next so it’s important to be prepared for all eventualities, as in any alpine environment. Arm sleeves or long-sleeved jersey can be good on the bike if the weather isn’t great.

“Lake Walchsee is a sheltered calm lake so preparation can focus on confidence in deep water rather than strong currents or waves. Be prepared for a non-wetsuit swim as the water temperature can get quite warm, depending on the weather. But the alpine climate means it can also be quite chilly so be prepared for all eventualities.

“The bike course has a total elevation of over 1,100m so hill training is a must, as is practicing fast technical descents so you don’t lose speed on the downhills. You can familiarise yourself with the course before race day by riding it on [virtual platform] Rouvy. The run around the lake is on a mix of road and off-road surfaces – it looks flat but is deceptively hilly.”

Challenge Gran Canaria

• Location Gran Canaria, Canary Islands, Spain
• Distance Olympic; Middle
• Date 26 April 2025

This Canary Island-set event has become a regular early season marker of race fitness for both age-groupers and pros alike over the last decade. The sheltered swim course and flat run leg shouldn’t pose too many problems, although it can be hot on the latter, but it’s the bike course that’ll test your race prowess. There are no outrageous climbs of note, just a relentlessly rolling coastal road that racers need to face not once, but four times. Pre-race turbo sets are nigh-on mandatory.

Mumbles Triathlon

• Location Mumbles, Gower
• Distances Sprint; Olympic; Middle
• Date 10 May 2025

This Ocean Lava-branded race is one of the first major open-water events of the UK season and regularly draws hundreds of racers to the gorgeous Gower peninsula. The waters of Swansea Bay will be chilly in early May, but it’s visibility from the rising sun that can cause problems for swimmers on the two-lap middle-distance course. Bring goggles with tinted lenses if you have them, while practise the art of sighting every fourth stroke in the pool. Aim to find a landmark in Swansea to swim toward if you can’t pick out the course markers and remember that the person whose feet you’re following might not be swimming in a straight line.

Windsor Triathlon

• Location: Windsor, Berkshire
• Distances: Sprint and Olympic
• Date: 15 June 2025

Set your alarm early for the notoriously early start of the Windsor Triathlon. Once you’re into the Thames for the swim, swim the downstream leg nearer the middle of the river and move closer to the side on the upstream return to make the most of the easterly river flow. And save some energy for the sneaky climb on Castle Hill on the run leg!

UK Ultimate Triathlon

• Location: Ellesmere, Shropshire
• Distances: 3.8km swim/180km bike/42.2km run
• Date: 29 June 2025

There’s little shade on the lakeside run course on this bargain Iron-distance race, so bring a cap and don’t forget the sun cream. The largely flat bike course is aerobar-friendly, so spend plenty of time honing your aero position and readying your body for the challenge before the race, both on the turbo and out on the open roads.

Challenge Roth

• Location: Roth, Bavaria
• Distance: 3.8km swim/180km bike/42.2km run
• Date: 6 July 2025

“Roth isn’t a flat ride, but it’s fast with a mix of steady climbs followed by quick descents,” says age-grouper Tom van Rossum. “With the cheering crowd, it’d be easy to light it up on the climbs but keep the pace steady and stick to your power/HR limits. Carving through the crowd up the Solarer Berg was a highlight! Enjoy these moments on the first lap because it feels a hell of a lot harder the second time around.”

SWYD Sprint triathlon

• Location Barry Island, South Wales
• Distance 750m swim/20km bike/5km run
• Date 24 August 2025

Both draft-legal and non-drafting races are on offer at this Barry Island beauty. Whichever you pick, the closed road bike leg has little in the way of elevation gain, with fast and flat laps around Barry. Remember to count those laps each time. Also don’t forget that registration is the day before.

Bala Triathlon

• Location Bala, Snowdonia
• Distances Sprint and Olympic
• Date 7 September 2025

It may be surrounded by the mountains of Snowdonia, but the long-running Bala Tri is a fast and largely flat affair for both speedsters and beginners. Prepare your soles for walking on rocks on the swim entry and exit, and embark on some cold-water acclimatisation and take a neoprene cap if you struggle with swimming in chilly waters.

Helvellyn Triathlon

• Location: Helvellyn, Cumbria
• Distances: TBC
• Date: 7 September 2025

“Don’t overdo the mountain training, just train hard,” says past winner Bonnie Van Wilgenburg on this classic Lake District toughie. “But if you only road run, head to the Lake District to practise some trail running and up and down the mountains on the course. Respect the mountains and the weather on race weekend; the mandatory kit list supplied by the organisers is there for a reason.”

Aviemore Triathlon

• Location Aviemore, Cairngorms
• Distances 1km swim/18km MTB 9km trail run
• Date 15 September 2025

For this southern softy at least, the waters of Loch Morlich are bracing, event in late summer, so embark on some cold-water prep before the event and take a neoprene swim hat. The off-road bike leg in Glenmore Forest boasts some technical sections: ready your MTB skills in advance and aim to recce both the bike and run course before race day.

Ironman Wales

• Location Tenby, Wales
• Distance 3.8km swim/180km bike/42.km run
• Date 21 September 2025

“The steepness of the climbs makes Tenby one of the hardest 180km Ironman courses,” says 39-time Ironman finisher Mark Kleanthous. “There are a few technical sections, especially ‘Heartbreak Hill’ at Saundersfoot. Drive this section before and mentally plan how you’ll tackle it in both the dry and wet. Don’t get sucked in by the crowds; hold back and ride within your ability.”

Castle Race Series: Hever Castle

• Location Hever, Kent
• Distances Multiple
• Date 27-28 September 2025

The Hever run course is tougher than the elevation profile suggests, with the mixed-terrain route liable to become muddy in places. Take one pair of road shoes and (if you own them) one trail pair with you, study the weather and check the route before deciding what’s best to wear. And save some energy for the sharp climb at the end of each lap.

Ironman World Championships

• Location Kona, Hawaii (women’s)
• Distance 3.8km swim/180km bike/42.2km run
• Date 11 October 2025

“There’s a huge buzz for the few days before the race,” says experienced coach and athlete Will Newbery, “but don’t panic train in a bid to emulate the super athletes when really you should be resting! On paper, the course should be fairly easy, but the heat and humidity adds a whole new dimension. The Queen K is like an oven with no wind. Be prepared for the only noise out there being your feet on the asphalt.”