A reliquary niche is a recessed opening built into a church wall, pillar or altar specifically to hold and display a relic, whether that relic is enclosed within an ornate reliquary container or, in some older or Eastern traditions, more directly visible or accessible to the faithful. Positioned deliberately to be seen, a reliquary niche is frequently framed with its own decorative surround, sometimes including a small canopy, an inscription naming the relic and its associated saint, or a grille allowing visual access while physically protecting the relic from damage or theft, since relics were historically valuable enough, both spiritually and, at times, financially, that security was a genuine practical concern for any church housing an important one.
The niche's placement within a church is rarely arbitrary: relics associated with the specific saint to whom the church is dedicated are often given the most prominent position, sometimes directly within or immediately beside the high altar itself, while relics of lesser or secondary significance to a given community might instead be housed in a side chapel or a niche along an aisle or ambulatory wall, so a church's pattern of reliquary niches can often be read as a kind of map of which saints and which relics its community considered most important to its own identity.