San Marino ( (listen), Italian: [sam maˈriːno]), officially the Republic of San Marino (Italian: Repubblica di San Marino; Romagnol: Ripóbblica d' San Marein), also known as the Most Serene Republic of San Marino (Italian: Serenissima Repubblica di San Marino), is a small country (and a European microstate) in Southern Europe enclaved by Italy. Located on the northeastern side of the Apennine Mountains, San Marino covers a land area of just over 61 km2 (24 sq mi), and has a population of 33,562.San Marino is a landlocked country but the northeastern end is within 10 kilometres (6.2 mi) of the Italian city of Rimini on the Adriatic Sea. The nearest airport is also in Italy. The country's capital city, the City of San Marino, is located atop Mount Titan, while its largest settlement is Dogana within the largest municipality of Serravalle. San Marino's official language is Italian.

The country derives its name from Saint Marinus, a stonemason from the then-Roman island of Rab in present-day Croatia. Born in AD 275, Marinus participated in the rebuilding of Rimini's city walls after their destruction by Liburnian pirates. Marinus then went on to found an independently ruled monastic community on Mount Titan in AD 301; thus, San Marino lays claim to being the oldest extant sovereign state, as well as the oldest constitutional republic.Uniquely, San Marino's constitution dictates that its democratically elected legislature, the Grand and General Council, must elect two heads of state every six months. Known as captains regent, the two heads of state serve concurrently and hold equal powers until their term expires after six months.

The country's economy is mainly based on finance, industry, services and tourism. It is one of the wealthiest countries in the world in GDP per capita, with a figure comparable to the most developed European regions.