The Hash House Harriers (abbreviated to HHH or H3) is an international group of social, non-competitive running and drinking clubs. Hashing has frequently been described as 'a drinking club with a running problem', and the social element of hashing is of equal importance to the running.

The organization of the Hash House Harriers is completely decentralized, with chapters (also commonly called kennels) having absolutely no formal regional or national offices or leadership structure. There are more than 1700 kennels with at least one Hash in virtually every major city in the world. Most hashes gather on a weekly, monthly or other regularly scheduled basis, with some occurring only sporadically, i.e. on Leap Year days, or Friday the 13th, when that occurs.

Several regonal directories or international directories have been published with Hash Contact information, although the Internet has become the primary source of hashing information.

The template for a hash run is for one or more hashers (the "hares") to lay out a running trail, which may include false trails, short cuts and trail breaks. These features are designed to keep the pack together regardless of fitness levels or running speed. The pack or 'hounds' follow the trail from check to check. From a check the pack will normally check out the surrounding terrain to attempt to find the continuation of the trail. A well-laid check will have the effect of allowing slower runners to catch up and rejoin the main pack, while the faster runners try to find the trail again.