Comarcas of the Basque Country

The autonomous Community of the Basque Country within Spain contains several "comarcas" or "eskualdeak" in the Basque language, referring to local districts, grouped into its three long-established provinces. 
The Basque Government's statistics department "Eustat" has divided the districts using a 20-comarca model (seven in Biscay, seven in Gipuzkoa and six in Álava) in its reports relating to the local economy and demographic trends on a consistent basis since at least 1999:
List of comarcas.
Alternative definitions.
As the comarca boundaries are not defined in law, various other broadly similar combinations have been published depending on the date, range and purpose of the data collection. Examples include:
Biscay province: the conurbations on either side of the Estuary of Bilbao within the Greater Bilbao comarca, known as the Left Bank and the Right Bank, are sometimes counted separately both from one another and from the city of Bilbao itself. Less commonly, the Getxo area on the Right Bank and the adjacent suburban Txorierri valley are grouped in a Uribe-Kosta district along with those in Mungialdea (referred to by Eustat as Plentzia-Mungia, with the term Uribe-Bertoe also used), while the Left Bank and the , the area's former mining zone, is merged into the mainly rural western Enkarterri comarca which previously governed the districts as a larger merindad, as was the case for the Right Bank in the Uribe merindad. The Hego Uribe area south of Bilbao tends to remain grouped with the city when other adjustments are made, or is linked with Arratia-Nervión if counted as an outlying zone. 
Gipuzkoa province: the southern portion of the Urola Kosta comarca (primarily Azpeitia and Azkoitia) has been listed separately as (Mid-Urola). Similarly, the western part of Goierri (around Zumarraga) has been recorded as the separate (Upper Urola) district. In the Donostialdea comarca (by far the most heavily populated, containing the city of San Sebastián and its satellite towns), the eastern part centred on Errenteria and Pasaia has been referred to as Oarsoaldea, and in some cases this has been combined with neighbouring Bidasoaldea, with the Oarsoaldea name even being adopted by some for this larger area. Less commonly, the name has been used to refer collectively to the cluster of towns south of San Sebastián (Lasarte-Oria, Hernani, Astigarraga, Andoain). 
Álava province: the main deviation from the Eustat comarcas (known here as "cuadrillas") is in the representation of the capital Vitoria-Gasteiz, which alternatively has its own district comprising its urban municipality alone. In this alignment the western part of the rump comarca is assigned to Gorbeialdea. The territory of Treviño is entirely surrounded by Álava, but is an exclave of the Province of Burgos and does not figure in the Basque considerations (its future status is a matter of dispute between the administrations).
Population contrasts.
As with the municipalities across Spain, the populations of each comarca vary widely; rural sectors of Álava cover only a few thousand residents each, while its capital Vitoria-Gasteiz (which is also a single municipality) is considered either to be in its own comarca or by far the most prominent component of the wider , containing over 250,000 residents under either arrangement. In Gipuzkoa, the Donostialdea comarca (population 330,000) includes not only the provincial capital San Sebastián (municipality population 185,000) but many of the smaller towns surrounding the city, leading to two further subdivisions being created in some contexts to represent these communities in a more balanced way. The most striking contrast is in Biscay, where the capital city Bilbao (again a single municipality with approximately 350,000 residents) is just one part of the Greater Bilbao comarca which has 850,000 within its boundaries. Bilbao's eight city districts are comparable in population to four of the province's other more rural comarcas, despite in theory being two administrative levels below.