San Marino, one of the smallest nations in the world and the world's oldest republic still in existence, is founded by Saint Marinus.

San Marino, officially the Republic of San Marino (RSM), is a landlocked country in Southern Europe, completely surrounded by Italy. Located on the northeastern slopes of the Apennine Mountains, it is the larger of two microstates within the Italian Peninsula, the other being Vatican City. San Marino is the fifth-smallest country in the world, with a land area of just over 61 square kilometres (24 sq mi) and a population of 34,042 as of 2025 which in 2026 dropped to 33,559. Its capital, the City of San Marino, sits atop Monte Titano, while its largest settlement is Dogana, in the municipality of Serravalle. San Marino claims to have been founded in AD 301 and to be the oldest extant sovereign state, and the oldest constitutional republic. It is named after Saint Marinus, a stonemason from the Roman island of Rab (in present-day Croatia), who fled persecution under Emperor Diocletian to have established a monastic community on Monte Titano, where he built a small chapel. The country has a rare constitutional structure: the Grand and General Council, a democratically elected legislature, selects two heads of state, the Captains Regent, every six months. They are chosen from opposing political parties, and serve concurrently with equal powers and preside over several institutions of state, including the Grand and General Council. Only the Federal Council of Switzerland follows this same structure, except with some modifications due to its immensely larger size.