The Bolder Boulder (styled as BOLDERBoulder and previously BolderBOULDER) is an annual 10-kilometer run in Boulder, Colorado. The most recent race featured over 54,000 runners, walkers, and wheelchair racers, making it the second largest 10k race in the US and the fifth largest road race in the world. It has one of the largest non-marathon prize purses in road racing. On March 16, 2020, organizers of the Bolder Boulder race initially decided to postpone the race, usually held on Memorial Day, until Labor Day due to COVID-19. On June 1, organizers then decided to cancel the 2020 race entirely.