San Marino (Serenissima Repubblica di San Marino) is the oldest republic in the world and the third smallest state in Europe, after Vatican and Monaco. It is an independent country, but it is entirely surrounded by Italy. It lies between the Emilia-Romagna and Marche regions, situated at an altitude ranging from 55m to 755m, on Monte Titano. San Marino has no coastline, but it is located just 10 km in a straight line from the Adriatic Sea.

The area of San Marino is 61 km², and it has a population of only around 34,000 inhabitants. The official language is Italian, and the official currency is the euro. No entry formalities are required to visit San Marino.

The territory of the state is divided into nine administrative units, called castelli ("castles"): Castello di San Marino, Castello di Serravalle, Castello di Borgo Maggiore, Castello di Faetano, Castello di Domagnano, Castello di Chiesanuova, Castello di Fiorentino, Castello di Montegiardino, and Castello di Acquaviva. The capital is Città di San Marino (also known as Castello di San Marino).

San Marino has been included on the UNESCO World Heritage List for its continuous existence as a free republic since the Middle Ages, as well as for the way it has preserved its historical appearance, untouched by urbanization.