Date
Sat Jan 10, 2026 (W)
Sun Jan 18, 2026 (NWF)
Sun Feb 8, 2026 (NWF)
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Sun Feb 22, 2026
Sun Feb 16, 2025 (W)
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Sat Feb 22, 2026
Location
Arvada, CO
Louisville, CO
Colorado Springs, CO
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Colorado Springs, CO
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Arvada, CO
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Arvada, CO
Sun Mar 2, 2025 (NWF)
Sat Mar 14, 2026 (W)
Sun Mar 22, 2026 (W)
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Sun Mar 23, 2025 (NWF)
That Dam 13.1 & 5k Crush that Dam
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Run Through Time Marathon, Half Marathon, 2-Mile
All-Out Spring Fever Half Marathon, 10k, 5k, 1 Mile
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Greenwood Village, CO
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Salida, CO
Golden, CO
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Fort Collins, CO
Sun Apr 13, 2025 (W)
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Sat Apr 12, 2025 (NWF)
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Sun Apr 19, 2026 (W)
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Sun Apr 13, 2025 (NWF)
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Sun Apr 13, 2025 (NWF)
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Sat Apr 18, 2026 (W)
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Sat Apr 25, 2026
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BSBC Boulder Rez Half Marathon, 10k, 5k
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Spring Fling Prairie Dog Half Marathon (3.5 hour time limit)
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Platte River Half Marathon & Relay (3 hour time limit)
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All-Out Beat the Heat Marathon, Half Marathon, 10k, 5k, 1 Mile
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Aurora, CO
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Boulder, CO
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Fort Collins, CO
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Arvada, CO
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Littleton, CO
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Westminster, CO
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Brighton, CO
Sun May 3, 2026
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Sun May 4, 2025
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Sat May 10, 2025
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Sat May 9, 2026 (T)
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Sun May 10, 2026 (T)
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Sat May 16, 2026
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Sun May 17, 2026
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Sat May 31, 2025
Colorado Marathon, Half Marathon, 10k, 5k
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Valkyrie Trail Race 50k, Marathon Half Marathon, 4mi
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Mountain Ridge Trail Race Half Marathon, 10k, 5k, 21 Miler
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Endure Trail Runs Half Marathon & 10k
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Denver Colfax Marathon & Half Marathon
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Fort Collins, CO
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Longmont, CO
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Firestone, CO
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Colorado Springs, CO
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Highlands Ranch, CO
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Divide, CO
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Aurora, CO
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Basalt, CO
Sun Jun 1, 2025
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Sun Jun 7, 2026 (W)
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Sat Jun 7, 2025 (W)
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Sat Jun 7, 2025
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Sat Jun 7, 2025
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Sun Jun 8, 2025
Sun Jun 15, 2025 (W)
Sat Jun 28, 2025 (W)
Colorado 13er (13.1mi), 10k, 5k
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Steamboat Marathon, Half Marathon & 10K
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All Out Summer Breeze Half Marathon, 10k, 5k, 1 Mile
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Louise Hammond Memorial Beardance Run Half Marathon, 10k, 5k
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Breckenridge Brewery Half Marathon & 5k
Estes Park Marathon, Half Marathon, 10k, 5k
Louisville, CO
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Steamboat Springs, CO
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Arvada, CO
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Durango, CO
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Towaoc, CO
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Littleton, CO
Estes Park, CO
Georgetown, CO
Fri Jul 4, 2025
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Sat Jul 12, 2025 (W)
Sat Jul 19, 2025
Sat Jul 19, 2025 (NWF)
Longmont, CO
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Westminster, CO
Aspen, CO
Castle Rock, CO
Sat Aug 2, 2025
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Sat Aug 2, 2025 (W)
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Sat Aug 2, 2025
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Sun Aug 3, 2025 (T)
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Sat Aug 9, 2025
Sat Aug 9, 2025
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Sat Aug 16, 2025 (W)
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Sun Aug 17, 2025 (NWF)
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Sat Aug 23, 2025
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Sat Aug 23, 2025 (NWF)
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Sat Aug 23, 2025
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Sat Aug 23, 2025
Vacation Races Rocky Mountain Half Marathon
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All-Out Runapalooza Half Marathon, 10k, 5k, 1 Mile
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Boulder Rez Marathon, 3/4 Marathon, Half Marathon, 10k, Relay
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The Emerald Mountain Epic Marathon & Half Marathon
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Fort Collins Human Race Half Marathon, 10k, 5k
Georgetown to Idaho Springs Half Marathon
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Staunton Rocks! Marathon & Half Marathon
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TBK Bank "Thirsty 13" Half Marathon
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Byers Peak Stampede Half Marathon & 5k
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Westminster Night Trail Race 50k, 35k, Half Marathon, 10k, 5k
Estes Park, CO
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Arvada, CO
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Boulder, CO
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Steamboat Springs, CO
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Fort Collins, CO
Georgetown, CO
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Ouray, CO
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Erie, CO
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Pine, CO
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Durango, CO
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Fraser, CO
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Westminster, CO
Mon Sep 1, 2025
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Sat Sep 6, 2025 (T)
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Sat Sep 13, 2025 (T)(NWF)
Sat Sep 13, 2025 (W)
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Sat Sep 13, 2025 (T)
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Sun Sep 14, 2025 (W)
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Sat Sep 20, 2025
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Sat Sep 27, 2025 (NWF)
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Sat Sep 27, 2025
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Sun Sep 28, 2025
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Sun Sep 28, 2025
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Tue Sep 30, 2025
Labor Day Half Marathon, 10k, 5k
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Ned * Ned Trailfest Half Marathon, 10k, 5k
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All-Out Fallfest Marathon, Half Marathon, 10k, 5k, 1 Mile
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Snow Mountain Ranch Trail Festival 50k, 33k, 21k, 10k, 5k
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Fall Equinox Marathon, Half Marathon & 5 Mile
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Beulah Challenge Half Marathon, 10k, 5k Trail Run & Walk
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"The Pioneer" Prairie Dog Half Marathon, 10k, 5k
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Red Feather Trail Jamboree Half Marathon
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Boulderthon Boulder Marathon, Half Marathon, 10k, 5k
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Center of the Nation Series Marathon, Half Marathon, 50/10/5k (day 1)
Parker, CO
Fort Collins, CO
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Nederland, CO
Buena Vista, CO
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Granby, CO
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Fort Collins, CO
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Beulah, CO
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Westminster, CO
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Snowmass Village, CO
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Red Feather Lakes, CO
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Boulder, CO
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Sterling, CO
Sat Oct 4, 2025
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Sun Oct 5, 2025
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Sun Oct 5, 2025
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Sun Oct 5, 2025
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Sat Oct 11, 2025
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Sat Oct 11, 2025
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Sun Oct 12, 2025 (W)
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Sat Oct 18, 2025
Colorado Springs Marathon & Half Marathon
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New Belgium Half Marathon & 5k
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Windsor Marathon, Half Marathon, 10k, 5k
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The Bear Chase Trail Half Marathon & 10k
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Long View Marathon & Half Marathon
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Breckenridge Road Marathon, Half Marathon & 10k
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Colorado Springs, CO
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Fort Collins, CO
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Windsor, CO
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Morrison, CO
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Fort Collins, CO
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Breckenridge, CO
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Westminster, CO
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Mancos, CO
Sun Nov 2, 2025
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Sat Nov 8, 2025 (T)
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Mon Nov 10, 2025 (W)
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Sat Nov 15, 2025
All-Out Kooky Spooky Half Marathon, 10k, 5k
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HRCA Backcountry Wilderness Half Marathon 2025 Registration
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Mainly Marathons Southwest Series 26.2mi, 13.1mi, 50/10/5k (day 2)
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Golden, CO
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Lone Tree, CO
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Durango, CO
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Louisville, CO
Sat Dec 6, 2025 (W)
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Sat Dec 6, 2025 (W)
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Sun Dec 7, 2025
All-Out Fa La La Half Marathon, 10k, 5k, 1 Mile
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Four Corners Quad Keyah Colorado Half Marathon
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Westminster, CO
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Ute Mountain, CO
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Pueblo, CO
Colorado Half Marathon Calendar event dates in grey are delinquent dates not updated by the race organizer yet. We strive to have dates 1 year out for Colorado half marathons, but have no control of when they set, announce or update their dates.
The Colorado Half Marathon Calendar is a complete simplistic listing of half marathons in Colorado. Currently the Colorado half marathon schedule has 2025 Colorado half marathons and 2026 Colorado half marathons as they roll in. Colorado half marathons 2025 & Colorado half marathons 2026 also identify trail half marathons and walker friendly half marathons by a (T) symbol and a (W) symbol. The (T) means it is a TRUE trail half marathon (off road, switchbacks, etc) and a (W) means it is truly "official walker friendly" requiring the half marathon to allow a minimum of 18:32 mile pace, minimum 4 hours for participants to finish the 13.1 mile distance.
The Colorado half marathon schedule of course features races such as Rock'n'Roll Denver Marathon and Rock'n'roll Denver Half marathon, along with a complete listing of Colorado half marathons, Denver half marathons, Ft. Collins half marathons, Colorado Springs half marathons, Boulder half marathons, Rocky Mountain half marathons, Vail half marathons, and many more half marathons in Colorado.
A half marathon is 13.1 miles (or in kilometers is a 21k). We understand sometimes there will be a slight margin of error up or down when runners run or walk any race distance, however our calendar only is a listing for true half marathons that do all they can to measure their course as an official half marathon 13.1 mile / 21k distance. Races that are not 13.1 miles, we encourage not to call their race a 1/2 marathon to lessen confusion for runners & walkers looking to participate in a true 1/2 marathon distance. Some runners don't care, but you'd be surprised how many that do.