The popularity of triathlon events continues to surge across the United Kingdom, reflecting a growing interest in multisport participation and personal endurance challenges. This report aims to provide a comprehensive overview of triathlon events scheduled to take place in the UK during the summer months of 2025, specifically June, July, and August. By categorizing these events by location, this analysis will offer potential participants a structured guide to help them identify suitable races based on their geographical preferences. The information presented in this report has been compiled from various triathlon event websites and calendars, providing a broad snapshot of the available opportunities.

June 2025 Triathlon Events by Region

2.1 South East England

The South East region of England appears to be a hub of triathlon activity in June 2025. Henley-on-Thames in Oxfordshire will host the Henley Triathlon 2025 on Saturday, June 1st . The consistent listing of this event across multiple platforms suggests its significance within the regional triathlon calendar. While one listing initially placed the Conquer The Chilterns Triathlon in June , further examination indicates it is more consistently scheduled for Saturday, July 12th , highlighting the importance of cross-referencing event dates. 

Windsor in Berkshire will see several events, starting with the Dorney Triathlon- June 2025 on Saturday, June 7th . Dorney Lake emerges as a frequently used venue for triathlons, likely due to its purpose-built facilities that cater well to the swim, bike, and run components of the sport. Later in the month, on Saturday, June 15th, Windsor will host the prestigious Royal Windsor Triathlon . The event's name and its location near Windsor Castle suggest a unique appeal, drawing participants to race in a historically significant setting . Also taking place in Windsor on the same day is The One for the Planet powered by Climategames.

Moving into Buckinghamshire, Marlow will host The One on the River - Marlow on Sunday, June 8th . The recurring title "The One on the River" with different locations suggests a series of events organized around a common theme related to waterside racing. In East Sussex, the Eastbourne Triathlon is scheduled for Sunday, June 8th . Notably, Eastbourne is also hosting a larger "Triathlon Festival" , hinting at a broader range of races and activities taking place around this time.

Bournemouth in Dorset will feature the Salty Sea Dog Duathlons & Triathlons - June on Saturday, June 14th . The inclusion of duathlons in this series, which appears across multiple summer months, indicates a broader appeal to multisport athletes who may prefer the run-bike-run format over a traditional triathlon. In Surrey, the Thorpe Park Sprint Triathlon is set for Saturday, June 29th . The location at a popular amusement park could attract participants looking to combine their race with a family outing or weekend getaway. Finally, in Bedfordshire, the ATW Stewartby Lake Triathlon & Aquabike will take place on Sunday, June 15th . The inclusion of an aquabike option (swim-bike) broadens the event's appeal to athletes who may not wish to participate in the running leg.

2.2 London

Currently, no specific triathlon events in London are explicitly listed within the provided information for June 2025.

2.3 South West England

The South West region will see triathlon activity in June, with events extending into Wales. Fishguard in Pembrokeshire, Wales, will host both the Fishguard Triathlon and The Wales Triathlon on Saturday, June 14th . It is likely these refer to the same event, potentially with different distance options or branding.

2.4 Midlands

In the Midlands, Woodstock will be the location for the Blenheim Palace Triathlon, taking place from Saturday, June 7th to Sunday, June 8th . Similar to the Royal Windsor Triathlon, the iconic setting of Blenheim Palace, a UNESCO World Heritage site, likely adds to the event's appeal, attracting participants who appreciate racing in scenic and historically significant locations. Further west in Tenby, GB, the Long Course Weekend – Wales will commence on Thursday, June 26th . The name "Long Course Weekend" suggests a multi-day event, likely featuring various endurance challenges beyond a single standard triathlon.

2.5 North of England

The North of England will host the Darwen Tri /Aquathlon/5k/10k - June 2025 in Darwen, GB, on Saturday, June 21st . The inclusion of an aquathlon and separate running races alongside the triathlon indicates a multisport event catering to a range of athletic interests and abilities, potentially creating a festival-like atmosphere.

2.6 Wales

As mentioned, Wales will host events in Fishguard and Tenby, covered in the South West and Midlands sections respectively due to the geographical grouping of the provided data.

2.7 Scotland

Based on the available information, no specific triathlon events in Scotland are listed for June 2025.

3. July 2025 Triathlon Events by Region

3.1 South East England

The South East continues to be a prominent location for triathlons in July. Windsor, Buckinghamshire, will host several events throughout the month, including the Dorney Evening Triathlon - July 2025 on Wednesday, July 2nd , The FixAddiction Triathlon on Saturday, July 5th , and two instances of the Dorney Triathlon on Sunday, July 13th and Sunday, July 27th . This continued presence of events at Dorney Lake reinforces its status as a key triathlon venue in the region.

Henley-on-Thames, Oxfordshire, will host the Conquer The Chilterns Triathlon on Saturday, July 12th , resolving the earlier date discrepancy. Bournemouth, now specified as Bournemouth, Christchurch and Poole, will feature the Salty Sea Dog Duathlons & Triathlons - July, also on Saturday, July 12th , continuing this multisport series. Marlow, Buckinghamshire, will again host The One on the River - Marlow on Sunday, July 13th .

Guildford in Surrey will host the Guildford Triathlon & Kids Aquathlon on Sunday, July 20th . The inclusion of a children's aquathlon alongside the main triathlon event indicates an effort to encourage participation among younger age groups and potentially create a family-friendly event atmosphere. Bedford will host the Bedford Team Triathlon Relays on the same day, Sunday, July 20th . The team relay format offers an alternative way to participate, allowing individuals to focus on a single discipline within the triathlon. Eastbourne, East Sussex, will host the TriBourne Festival of Endurance on Sunday, July 20th . Similar to the Long Course Weekend, a "Festival of Endurance" likely encompasses multiple long-distance events or formats. Finally, The Felixstowe Triathlon will take place in Felixstowe, GB, on Saturday, July 19th .

3.2 London

No specific triathlon events in London are listed in the provided information for July 2025.

3.3 South West England

The South West region will see the Conquer the Chilterns Triathlon, also listed under the South East, taking place in Henley-on-Thames, Oxfordshire . Additionally, the 2025 Upton Triathlon is scheduled for Friday, July 11th in Worcester, GB.

3.4 Midlands

The Midlands will feature the Outlaw Half Holkham Weekend 2025 in Wells-next-the-Sea, GB, starting on Saturday, July 5th . The "Outlaw Half" branding suggests this is part of a series of middle-distance triathlon events. Later in the month, the Outlaw Nottingham Weekend 2025 will commence on Friday, July 25th in Holme Pierrepont, GB, further establishing the presence of this middle-distance race series.

3.5 North of England

The Ripon Triathlon Festival is scheduled to take place in Ripon, North Yorkshire, UK, from Saturday, July 12th to Sunday, July 13th , indicating a weekend dedicated to triathlon racing with potentially various distances and formats on offer.

3.6 Wales

No specific triathlon events in Wales are listed in the provided information for July 2025.

3.7 Scotland

Based on the available information, no specific triathlon events in Scotland are listed for July 2025.

4. August 2025 Triathlon Events by Region

4.1 South East England

August sees continued triathlon activity in the South East. Windsor, Berkshire, will host the Dorney Triathlon - August 2025 on Friday, August 8th and the Dorney Evening Triathlon - August 2025 on Wednesday, August 27th , maintaining Dorney Lake's role as a key venue. London will host the prominent London T100 Triathlon 2025 from Saturday, August 9th to Sunday, August 10th . This event is presented as a major, iconic race, utilizing closed roads within the city and attracting a large number of participants.

Bournemouth, Bournemouth, Christchurch and Poole, will feature the Salty Sea Dog Duathlons & Triathlons - August on Saturday, August 9th , continuing the monthly series. Chertsey, Surrey, will host the Thorpe Park Sprint Triathlon on Saturday, August 31st . Hove, East Sussex, will see the Brighton and Hove Triathlon also on Saturday, August 31st . Finally, the HSV Sprint Triathlon & Aquabike is scheduled for Sunday, August 31st in Hatfield, Hertfordshire.

4.2 South West England

No specific triathlon events in the South West England are listed in the provided information for August 2025.

4.3 Midlands

The Midlands will host the Endorphin Sport Belvoir Castle Multisport Weekend 2025 in Grantham, GB, starting on Friday, August 29th . Similar to Blenheim and Windsor, Belvoir Castle offers a historic and scenic backdrop for a multisport event, which is also noted for being beginner-friendly . Peterborough, Northamptonshire, will host the ATW Oundle Triathlon and the ATW Oundle Children’s Triathlon, both on Sunday, August 17th.

4.4 North of England

Masham, GB, will be the location for The Long Course Weekend - Yorkshire, starting on Thursday, August 28th , extending the Long Course Weekend series to another region. York will host the York Triathlon 2025 on Sunday, August 17th.

4.5 Wales

Wales will feature the Craft Snowman Triathlon & Duathlon, Snowman Swim & Ogwen Yr Helgi Du Trail Runs in Betws-y-Coed, Clwyd, from Saturday, August 2nd to Sunday, August 3rd . The variety of events listed suggests a broader outdoor sports festival rather than solely a triathlon.

4.6 Scotland

Lochore in Crosshill, GB, will host the Lochore Off-Road Triathlon Festival 2025 on Saturday, August 30th . The "Off-Road" designation indicates that this event will likely involve swimming in open water, mountain biking, and trail running, offering a different experience from standard road-based triathlons.  

5. Detailed Event Information (Selected Key Events)

5.1 London T100 Triathlon 2025 (August 9-10, London)

The London T100 Triathlon offers a range of distances, catering to various levels of experience. Individual participants can choose from the 100km distance, comprising a 2km swim, 80km bike ride, and 18km run; the Olympic distance, with a 1.5km swim, 40km bike ride, and 10km run; or the Sprint distance, featuring a 0.75km swim, 20km bike ride, and 5km run . Team relay options are also available for the Olympic and Sprint distances, using the same segment distances as the individual events . Registration for the 2025 event is currently open . The availability of these varied distances, including the unique 100km option, makes the London T100 accessible to both novice and seasoned triathletes.

5.2 Blenheim Palace Triathlon (June 7-8, Woodstock)

The Blenheim Palace Triathlon presents a diverse selection of race formats. Participants can compete in the Super Sprint (400m swim, 13.2km bike, 2.9km run), the Sprint (750m swim, 19.8km bike, 5.4km run), or as part of a Sprint Relay team . For those seeking a greater challenge, the Weekend Warrior option allows participants to complete as many back-to-back Sprint triathlons as possible over the two-day festival . Additionally, the event includes duathlon options: a Full Duathlon (10km run, 44km bike, 5km run) and a Half Duathlon (5km run, 22km bike, 5km run) . Registration is available through the "ENTER NOW" buttons on the event website . The inclusion of duathlons alongside the various triathlon distances broadens the event's appeal to a wider range of multisport enthusiasts.

5.3 Eastbourne Triathlon (June 8, Eastbourne)

The Eastbourne Triathlon offers several events with varying distances. These include the Novice Super-Sprint (400m swim, 9km bike, 2.4km run), the Sprint (750m swim, 18.3km or 20km bike, 5km run), and the Standard distance (1500m swim, 40km or 41.5km bike, 10km run) . A 100k Triathlon is also mentioned , though specific details were not available in the provided information. Furthermore, relay, duathlon (run/bike/run), and aquathlon (swim/run) options are available for both the Sprint and Standard distances . Registration can be accessed via a provided link . The comprehensive range of distances and multisport options makes the Eastbourne Triathlon suitable for athletes of all experience levels.

5.4 Royal Windsor Triathlon (June 15, Windsor)

The Royal Windsor Triathlon primarily focuses on the classic Sprint and Olympic distances. The Sprint distance comprises a 750m swim, a 20km bike ride, and a 5km run, while the Olympic distance involves a 1.5km swim, a 40km bike ride, and a 10km run . A Super Sprint distance (400m swim, 10km bike, 2.5km run) is also mentioned as a common triathlon distance and is likely offered, though not explicitly confirmed for the 2025 event in all sources. While the event website was inaccessible , registration is mentioned as open . The focus on standard triathlon distances makes this event a popular choice for a wide range of competitive triathletes.

5.5 Outlaw Half Holkham Triathlon (July 5, Wells-next-the-Sea)

The Outlaw Half Holkham Triathlon offers a middle-distance option consisting of a 1.2-mile swim, a 56-mile bike ride, and a 13.1-mile run . Additionally, the event includes the Outlaw Gravel Sprint on Saturday, featuring a 750m swim, a 19km off-road bike course, and a 5km run . An Outlaw Half Aquabike option, which includes the 1900m swim and 56-mile bike ride without the run, is also available . Relay options are offered for the Outlaw Half distance . Registration can be accessed via a provided link . The variety of options, including the half-Ironman distance, a gravel sprint, and an aquabike, caters to different preferences within the longer-distance triathlon community.

6. General Registration Process for UK Triathlon Events

Information regarding the general registration process across all UK triathlon events is somewhat limited within the provided data, with most details focusing on specific events. However, the snippets offer some insights. Registering with the national governing body, British Triathlon, appears to be a common step, particularly for those participating in competitive events or requiring race licenses . For individuals who do not hold a full race license, a one-day race pass can often be purchased through the British Triathlon website . The typical process after entering an event involves receiving confirmation emails and race day information, including race numbers and start times, via email approximately 7 to 10 days prior to the event . Race number collection usually takes place at registration on the day of the event, where participants may also receive race packs containing stickers and wristbands . For those aiming to qualify for the Great Britain Age-Group Team, the process involves joining a Home Nation association (Triathlon England, Triathlon Scotland, or Welsh Triathlon) and registering for a specific Championship event . While specific registration procedures may vary between different event organizers, online registration platforms are the standard method, and affiliation with British Triathlon, either through membership or a day license, is often required, especially for sanctioned races.

7. Summary Table of Key Triathlon Events (Summer 2025)

8. Conclusion

The analysis of available information reveals a significant number of triathlon events scheduled across the United Kingdom during the summer of 2025. These events span various regions, dates, and cater to a wide range of fitness levels and preferences, from beginner-friendly sprint distances to challenging middle-distance and multi-day endurance formats. Iconic locations such as Windsor and Blenheim Palace, as well as dedicated triathlon venues like Dorney Lake, host multiple events, suggesting a strong connection between the sport and these appealing settings. The presence of established race series like the Outlaw Half and "The One on the River," along with multisport festivals, indicates a vibrant and diverse triathlon community in the UK. Potential participants are encouraged to visit the official websites of specific events for the most current and detailed information regarding race distances, registration procedures, and any potential schedule changes. Additionally, checking the British Triathlon website can provide valuable resources on licenses, affiliated events, and further guidance for those looking to participate in triathlon races in the UK.