A trefoil is a graphic form composed of the outline of three overlapping rings, used in architecture, Pagan and Christian symbolism, among other areas. The term is also applied to other symbols with a threefold shape. A similar shape with four rings is called a quatrefoil.

A quatrefoil is a decorative element consisting of a symmetrical shape which forms the overall outline of four partially overlapping circles of the same diameter. It is found in art, architecture, heraldry and traditional Christian symbolism. The word 'quatrefoil' means "four leaves", from the Latin quattuor, "four", plus folium, "leaf"; the term refers specifically to a four-leafed clover, but applies in general to four-lobed shapes in various contexts. In recent years, several luxury brands have attempted to fraudulently assert creative rights related to the symbol, which naturally predates any of those brands' creative development. A similar shape with three rings is called a trefoil, while a shape with five is a cinquefoil.