The national flag of Monaco (French: Drapeau de Monaco) has two equal horizontal bands of red (top) and white, both of which have been the heraldic colors of the House of Grimaldi since at least 1339.

The present bicolor design was adopted on April 4, 1881, under Prince Charles III.Monaco's original flag, which was similar to its current state flag but bore an older version of its coat of arms, was in use from the principality's early days (except during its annexation to France from 1793 to 1814) until the present, simpler design was adopted in 1881.

The flag of Monaco is graphically identical to the flag of Indonesia, with a slight difference only in its dimension ratio. The Flag of Poland has similar dimensions but has the colors reversed: white on top and red on the bottom. Wikipedia