San Sebastian is a coastal city and municipality located in the Basque Autonomous Community, Spain. It lies on the coast of the Bay of Biscay, 20 km (12 miles) from the French border. The capital city of Gipuzkoa, the municipality's population is 186,095 (2015), with its metropolitan area reaching 436,500 (2010). Locals call themselves donostiarra (singular), both in Spanish and Basque.

The main economic activities are commerce and tourism, and it is one of the most famous tourist destinations in Spain. Despite the city’s small size, events such as the San Sebastian International Film Festival have given it an international dimension. San Sebastian, along with Wroclaw, Poland, was the European Capital of Culture in 2016.

In spite of appearances, both the Basque form Donostia and the Spanish form San Sebastian have the same meaning of Saint Sebastian. The dona/done/doni element in Basque place-names signifies "saint" and is derived from Latin domine; the second part of Donostia contains a shortened form of the saint's name. There are two hypothesis regarding the evolution of the Basque name: one says it was *Done Sebastiane > Donasa(b)astiai > Donasastia > Donastia > Donostia, the other one says it was *Done Sebastiane > *Done Sebastiae > *Done Sebastie > *Donesebastia > *Donasastia > *Donastia > Donostia.

The city is in the north of the Basque Autonomous Community, on the southern coast of the Bay of Biscay. San Sebastian's picturesque shoreline makes it a popular beach resort. The seaside environment is enhanced by hilly surroundings that are easily accessible, i.e., Urgull (at the heart of the city by the seashore), romantic Mount Ulia extending east to Pasaia, Mount Adarra rising proud far on the south and Igeldo, overlooking the bay from the west.

The city sits at the mouth of the River Urumea, Donostia having been built to a large extent over the river's wetlands during the last two centuries. In fact, the city centre and the districts of Amara Berri and Riberas de Loiola lie on such terrain and the former bed of the river, diverted to its current canalized course in the first half of the 20th century.

As a result of Donostia's sprawling in all directions, first into the flatlands shaped by the river Urumea and later up the hills, new districts arose after the walls of the city were demolished in 1863. The first expansion of the old town stretched out to the river's mouth, on the old quarter called Zurriola (a name later given by Council decision to the sand area and the avenue across the river).

The orthogonal layout nowadays making up the city centre (the Cortazar development) was built up to 1914 (first phase finished) much in tune with a Parisian Haussmannian style. The arcades of the Buen Pastor square were fashioned after the ones of the Rue de Rivoli, with the Maria Cristina Bridge being inspired by the Pont Alexandre III that spans the Seine. The Estacion del Norte train station standing right across the bridge was inaugurated in 1864 just after the arrival of the railway to San Sebastian, with its metallic roof being designed by Gustave Eiffel. Donostia's central bus station is located underground adjacent to the train station.