Which country has a non-rectangular national flag?

Nepal has a non-rectangular national flag. Its distinctive design consists of two joined triangular pennants, forming a concave, double-pennon shape rather than the rectangle or square used by almost every other national flag.

The modern flag uses a crimson-red field, a deep-blue border, and white symbols of the moon and sun. Red represents bravery and is also associated with Nepal's national flower, the rhododendron; blue traditionally represents peace. The moon and sun symbolize qualities associated with the Nepali people and the enduring nature of the nation.

Nepal's current flag was standardized and adopted on December 16, 1962. Civil engineer Shankar Nath Rimal refined the traditional double-pennon design, while the older versions of the flag included human faces on the sun and moon. Those faces were removed during modernization.

Qatar, Vatican City, and Switzerland have unusual proportions or square-like flags, but their national flags are still rectangular or square. Nepal's constitution even includes a precise geometric construction method so the flag can be drawn and manufactured consistently rather than approximated as a simple triangle.