The triforium, a word from the medieval Latin triforium,[1]​ coming in turn from the Latin transforatum ('perforated'), is an architectural element located on both walls of the central nave "Nave (architecture)"), just above the arcades that overlook the side naves. It consists of a line of openings, usually twinned "Geminated (architecture)"), open in the thickness of the walls.[1]​.

It should not be confused with the tribune, which is a corridor "Aisle (architecture)") whose width coincides with that of the side nave on which it is built. When the tribune and clerestory coincide, that constitutes the second floor, with the clerestory being the third.

In cathedrals located on pilgrimage routes such as the Camino de Santiago, the stands usually had the function of housing pilgrims, in addition to providing space for a larger number of attendees at religious celebrations.