Nepal has the world's only national flag with a non-rectangular shape.
Nepal's flag consists of two joined triangular pennants, often described as a double pennon. Its crimson-red field is bordered in blue and carries white symbols of the moon and sun.
The modern flag was adopted in 1962, although its two-triangle design comes from older South Asian pennants. The moon and sun traditionally express the hope that Nepal will endure as long as these celestial bodies.
Switzerland and Vatican City have square national flags, which are unusual but still rectangular. Nepal's distinctive outline is the key distinction: it is made from two triangles rather than a four-sided quadrilateral. The constitution specifies the flag's geometric construction in unusual detail, including proportions and the method used to draw its symbols.