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Triathlon Calendar near Thornton 2025-2026

Explore the top triathlons near Thornton for 2025-2026! We've gathered 95 exciting races in the area. Check out our detailed list below to find your next local race.

July 2025
Jul
27
Sunday

Spirit of the West 5K

5 km
August 2025
Aug
1
Friday

RMRR Trophy Series

5 km
Aug
2
Saturday

All-Out Runapalooza

5 km 10 km 13 mi
Aug
2
Saturday

Boulder Rez Marathon

Trail Run 10 km 13 mi 31 km 26 mi
Aug
2
Saturday

Unicorn 5k - Highlands Ranch

5 km
Aug
3
Sunday

Bound for Boston Marathon - Denver

13 mi 26 mi
Aug
9
Saturday

Holy Cow Trail Stampede

Trail Run 5 km
Aug
9
Saturday

Dog Days of Summer

3 mi
Aug
9
Saturday

Dirt Circus - Boulder

Trail Run 4 mi
Aug
16
Saturday

Summer Sizzler - Denver

5 km 10 km 15 km
Aug
17
Sunday

Erie Half

5 km 13 mi
Aug
23
Saturday

Westminster Night Trail

Trail Run 5 km 10 km ... 35 km 50 km
Aug
23
Saturday

Boulder Sunset Run

5 km 10 km
September 2025
Sep
1
Monday

Labor Day Half Marathon

5 km 10 km 13 mi
Sep
5-6
Fr - Sa

American Heroes Run

Trail Run 5 km 9 mi ... 100 mi 24 hr
Sep
6
Saturday

HRCA Wildcat Mountain Trail Race

Trail Run 10 km 10 mi
Sep
7
Sunday

Denver Rocks Run 10K

5 km 10 km
Sep
7
Sunday

Conservation Colorado 5k

5 km
Sep
7
Sunday

RMRR Trophy Series

5 km 10 km
Sep
13
Saturday

All-Out Fall Fest

5 km 10 km 13 mi
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