Trail Races & Ultramarathons Near Boulder, CO

As of October 6, 2026, Crewable lists 22 upcoming trail races and ultramarathons near Boulder, CO from October 2026 to September 2027. The next is Rocky's Backyard Ultra on October 10 in Estes Park, CO. Registration is open for 7. 2 advertise prize money.

Updated Oct 5, 2026Sources: UltraSignup, RunSignUp, UTMB, race organizers and race websites

With aid station data

2 aid

Sat, Oct 17in 11 days

Indian Creek Trail Runs

Sedalia, CO

50 mi55K+2Prize money

Open until Oct 14from $60

13 aid

Sat, Oct 17in 11 days

Blue Sky Trail Marathon & Half Marathon

Fort Collins, CO3,500 ft gain

MarathonHalf Marathon

Open until Oct 17from $110

7 aid

Sat, Nov 14in 39 days

Louisville Trail Race

Louisville, CO501 ft gain

Half Marathon10K+1

Open until Nov 9from $55

3 aid

Sat, Nov 7in 32 days

Marathon At The MAC

Castle Rock, CO

MarathonHalf Marathon+1

Closedfrom $50

1 aid

Sat, Oct 31in 25 days

11th Hour Bear Creek Backyard Ultra

Lakewood, CO

Backyard Ultra

Closes Oct 28from $60

1 aid

Sat, Oct 10in 4 days

Rocky's Backyard Ultra

Estes Park, CO

Backyard Ultra$1,000 purse

Closes Oct 9from $130

Race calendar

October 2026

7 races

Oct10Sat
Rocky's Backyard Ultra
Estes Park, CO
Backyard Ultra$1,000 purse
Closes Oct 9from $130
Oct17Sat
Blue Sky Trail Marathon & Half Marathon
Fort Collins, CO3,500 ft gain
MarathonHalf Marathon
Open until Oct 17from $110
Oct17Sat
Indian Creek Trail Runs
Sedalia, CO
50 mi55K+2Prize money
Open until Oct 14from $60
Oct24Sat
The Barnyard Backyard Ultra
Erie, CO
Backyard Ultra
Closes Oct 21from $125
Oct25Sun
Beware the Bear Trail Races
Lakewood, CO800 ft gain
15K5K
Closes Oct 25from $10
Oct31Sat
11th Hour Bear Creek Backyard Ultra
Lakewood, CO
Backyard Ultra
Closes Oct 28from $60
Oct31Sat
HRCA Backcountry Wilderness Half Marathon
Lone Tree, CO
Half Marathon
Open until Oct 31from $75

November 2026

6 races

Nov7Sat
Colorado 24 Hour Run
Fort Collins, CO
24 hr12 hr+1
Open until Oct 31from $125
Nov7Sat
Marathon At The MAC
Castle Rock, CO
MarathonHalf Marathon+1
Closedfrom $50
Nov7Sat
Sandstone Sixer
Larkspur, CO
6 hr
Nov7Sat
Turkey Trails- Denver
Littleton, CO
Half Marathon10K+2
Open until Nov 8from $17
Nov14Sat
Louisville Trail Race
Louisville, CO501 ft gain
Half Marathon10K+1
Open until Nov 9from $55
Nov15Sun
Mountain Peacock 50k
Golden, CO
50K

December 2026

3 races

Dec5Sat
Sawmill Trail Runs
Pine, CO
50K16 mi+1
Open until Dec 3from $60
Dec5Sat
Thumbs Up Vertical Challenge
Estes Park, CO
8 hr
Dec19Sat
Santa's Summit Slam
Estes Park, CO
10K

January 2027

1 race

Jan9Sat
Frozen Devil's Head
Sedalia, CO
21.6 mi

February 2027

1 race

Feb6Sat
Sourdough Snowshoe Race
Nederland, CO
30K18K

May 2027

1 race

May22Sat
Samson's Revenge
Estes Park, CO
50K25K+1

July 2027

1 race

Jul26Mon
The Summit 200
Frisco, CO

August 2027

1 race

Aug7Sat
Winter Park Trail Runs
Winter Park, CO
50K21K+1

September 2027

1 race

Sep2Thu
Front Range Ultra Dayze
Loveland, CO
100 hr3 days+6

Quick answers

What is the next trail race or ultramarathon near Boulder, CO?

Rocky's Backyard Ultra, on Saturday, October 10, 2026, in Estes Park, CO. Distances: Backyard Ultra.

What is the closest trail race or ultramarathon to Boulder?

Louisville Trail Race in Louisville, CO, about 8 miles from Boulder, on November 14, 2026.

How many trail races and ultramarathons near Boulder, CO have open registration?

7 of the 22 list registration as open as of October 6, 2026, including Blue Sky Trail Marathon & Half Marathon, Indian Creek Trail Runs and HRCA Backcountry Wilderness Half Marathon.