Overview The Boston Triathlon is the city's only triathlon: on a Sunday in late August racers swim in Dorchester Bay off Carson Beach in South Boston, ride Day Boulevard with the whole bike course closed to cars and run by state troopers, and finish cross-country through Moakley Park. Sunday carries an Olympic distance (1.5K swim, 35K bike, 10K run) and a sprint (750 meters, 17.5K, 5.5K), with two- and three-person relays and a team challenge for groups of seven or more. Saturday is Kids Day, free for children. The 2026 race was the 18th. The Boston Triathlon Foundation, a 501(c)(3), runs training clinics and competitions for children and adults around it. On site The start and finish sit on DCR Carson Beach and Mother's Rest fields. Saturday opens with Kids Day in the morning, a Splash and Dash for ages 7 to 15 in four age groups plus a Kids Fun Run, then packet pickup, bike racking, an athlete briefing and an evening swim clinic. On Sunday the Olympic wave goes off at 7 and the sprint at 8:45, and the post-race party opens in the beer garden at 10, two hours before the awards. In 2024 the professional supertri series raced its Boston round on the same weekend, after the age groupers. Audience The race sets out to bring in people triathlon usually misses. It runs women-only waves, says 99 percent of its coaches are women, cuts entry in half for athletes under 23, adds high school and collegiate waves, and gives free or deep-discount entries to people in need. Racers have come from all 50 states and 50 countries, and many race in groups: running clubs, company teams, the Boston Fire Triathlon Team, Boston EMS and the police department. Talent and Influencers Racers and guests have included Jeremy Swayman of the Boston Bruins, Olympian Sarah True, USA Triathlon Hall of Famer Karen Smyers, Dave McGillivray, Becca Pizzi, Congressman Stephen Lynch and former mayor Marty Walsh. Track record USA Triathlon recognized the free Kids Day Splash and Dash and Fun Run as the most successful of its kind in the country, and 2025 was its 11th year. The race is a founding partner, with the City of Boston and Blue Cross Blue Shield of Massachusetts, of Swim Safe Boston, which had given more than 7,000 children free swim lessons by 2025. Columbia Threadneedle Investments CEO Ted Truscott: "Partnering with the Boston Triathlon has significantly increased the awareness of Columbia Threadneedle Investments in the city of Boston and beyond." Brand presence Partners race as well as sponsor. At past editions Boston Medical Center's Team BMC and a Columbia Threadneedle team were on the course and in the village across both days, handing out information on addiction programs, and Boston Medical Center is the race's fundraising partner. Meet Boston was host partner for the 2025 race. Company teams of seven or more can enter the team challenge for prize money.