# List of municipalities in Biscay

Biscay is a province in the autonomous community of the Basque Country, Spain, that is divided into 113 municipalities. As of the 2023 Spanish census, the province is the tenth largest by population, with 1,153,282 inhabitants, and the second smallest by land area, spanning 2,215.55 square kilometres (855.43 sq mi). Municipalities are the basic local political division in Spain and can only belong to one province. They enjoy a large degree of autonomy in their local administration. Amongst other tasks, they are in charge of urban planning, water supply, lighting, road network, local police, and firefighting.
The organisation of municipalities in Spain is outlined in a local government law (Spanish: Ley 7/1985, de 2 de abril, Reguladora de las Bases del Régimen Local; transl. Law 7/1985, of 2 April, Regulating the Bases of the Local Administration) passed on 2 April 1985 and finalised by an 18 April 1986 royal decree. The Statute of Autonomy of the Basque Country of 1979 also contains provisions concerning the relations between the municipalities and the autonomous government of the Basque Country. All citizens of Spain are required to register in the municipality in which they reside. Each municipality is a corporation with independent legal personhood: its governing body is called the ayuntamiento (municipal council or corporation), a term often also used to refer to the municipal offices (city and town halls). The ayuntamiento is composed of the mayor (Spanish: alcalde), the deputy mayors (tenientes de alcalde) and the plenary assembly (pleno) of councillors (concejales). Municipalities are categorised by population for the purpose of determining the number of councillors: three when the population is up to 100 inhabitants, five for 101–250, seven for 251–1,000, nine for 1,001–2,000, eleven for 2,001–5,000, thirteen for 5,001–10,000, seventeen for 10,001–20,000, twenty-one for 20,001–50,000, and twenty-five for 50,001–100,000. One councillor is added for every additional 100,000 inhabitants, with a further one added when the number of councillors based on this methodology would be even in order to prevent tied votes.
The mayor and the deputy mayors are elected by the plenary assembly, which is itself elected by universal suffrage. Elections in municipalities with more than 250 inhabitants are carried out following a proportional representation system with closed lists, whilst those with a population lower than 250 use a block plurality voting system with open lists. The plenary assembly must meet periodically at the seat of the ayuntamiento, with meetings occurring more or less frequently depending on the population of the municipality: monthly for those whose population is larger than 20,000, once every two months if it ranges between 5,001 and 20,000, and once every three months if it does not exceed 5,000. Many ayuntamientos also have a local governing board (Spanish: junta de gobierno local), which is named by the mayor from amongst the councillors and is required for municipalities of more than 5,000 inhabitants. The board, whose role is to assist the mayor between meetings of the plenary assembly, may not include more than one third of the councillors.
The largest municipality by population in the province of Biscay as of the 2023 Spanish census is Bilbao, its capital, with 345,235 residents, while the smallest is Arakaldo, with 162 residents. The largest municipality by area is Karrantza Harana/Valle de Carranza, which spans 137.82 km², while Lanestosa is the smallest at 1.14 km².

## Municipalities

* Most populous municipalities in Biscay
* Bilbao is the province's capital and largest municipality by population.
* Barakaldo, the second most populous municipality in Biscay
* Getxo is Biscay's third largest municipality by population.
* Santurtzi, Biscay's fourth largest municipality by population
* Portugalete is the fifth most populous municipality in Biscay.
* Basauri is the province's sixth largest municipality by population.
† Provincial capital