San Marino claims to be the world's oldest republic, and its flag carries emblems that have been in use for centuries.
Adopted in 1862, older in practice
The flag took its current form on 6 April 1862, though the symbols on it are much older. The republic dates itself to 301 AD, and earlier versions of the design were associated with the Arengo, the town's chief assembly. The 1862 adoption coincided with San Marino being recognized as a sovereign state by the European powers of the day.
Since then the changes have been small and mostly confined to the coat of arms, adjusted here and there as governments and diplomatic arrangements shifted.
White above blue, with three towers
The flag is two horizontal bands, white on top and light blue below, with the coat of arms in the center. White is for peace and purity, which suits a republic that has stayed neutral toward its neighbors for a long time. Blue is for liberty and for the sky over the mountains.
The arms repay a close look. The shield shows three towers on three peaks: Guaita, Cesta, and Montale, the fortifications on Monte Titano. Each tower is crowned with an ostrich feather for freedom. Below the shield, an oak branch and a laurel branch are bound together, oak for stability and laurel for honor. A crown sits above for sovereignty, and a scroll below reads "Libertas".
Usage
The flag is displayed at government buildings, public institutions, and official events at home and abroad. Rules govern its condition and handling: it must be in good repair, must never touch the ground, and is hoisted at sunrise and lowered at sunset.
There are two versions. The civil flag has no coat of arms and is the one used by citizens. The state flag carries the arms and appears at official functions, in schools, and at community festivals.
Similar flags or influences
The blue and white bicolor puts San Marino in company with Guatemala and the United Nations, though nothing else about the flags matches. The coat of arms is where European heraldic tradition shows most clearly.
References
[1] San Marino Republic Official Website: https://www.pa.sm
[2] North American Vexillological Association - "Flags of the World": https://www.nava.org
[3] "Flags through the Ages and Across the World" by Whitney Smith
[4] Flag Institute: https://www.flaginstitute.org