The adidas Shamrock Run is the largest running and walking event in Portland and the third largest race in the Western United States. This race is one of the few in the Pacific Northwest to offer a complete variety of distance options to racers including a 5k, 8k, 15k, and a half marathon.

This race has a cap of 35,000 runners (3,000 cap on the half marathon) and does have a history of selling out. Runners who do get a spot in the Shamrock Run can expect to tackle a scenic urban course in and around downtown Portland amongst a sea of green clad racers.