What micro-state is considered to have the oldest constitution still in effect?

The story behind the answer

San Marino is correct: its Constitution—codified in the Statutes of 1600—remains in force, making it the world’s oldest written constitution still operative. Those statutes set up core institutions like the Grand and General Council and the dual heads of state, the Captains Regent, elected every six months.

Context helps: although San Marino traces its origin to a monk, Saint Marinus, in 301 CE, it was the 1600 statutes that formally defined its government. By contrast, Monaco (1962), Andorra (1993), and Saint Kitts and Nevis (1983) have much newer constitutions. Memory tip: think of the tiny hilltop republic on Mount Titano as a living time capsule—its 17th-century rules still guide a modern state.