Basconia

Founded in 1913 and named after a local iron and steel-working works [eu] (later owned by the Altos Hornos de Vizcaya company), Basconia reached the national third level (Tercera División) thirty years later. The club played in the second tier for six seasons (1957–63), but this was before the creation of the regionalised new third division in the 1970s.

In 1997, Basconia became Basque neighbours Athletic Bilbao's feeder club, not being eligible for promotion if the reserves, Bilbao Athletic, playing in the level above, did not attain the same goal. The primary function of the agreement is to aid the development of young players in a challenging environment while remaining in the same group under the close guidance of the parent club; a number of teenagers who spent a season at Basconia became professionals at Athletic Bilbao, eventually playing in La Liga and UEFA competitions. In January 2020 it was confirmed that the partnership, due to expire that summer, had been renewed for another three years to 2023.

Basconia's place in Athletic's club structure means that the squad changes greatly each season. About half of the players move up to play for Bilbao Athletic, or go out on loan to other local clubs playing at Segunda División B level. They are replaced by graduates, usually 17 or 18 years old, from the previous year's Juvenil A team. The squad is normally expanded further with new signings from the regions's youth clubs, most notably Danok Bat and Antiguoko.

Although Athletic Bilbao control the main squad's players and coaching personnel, Basconia retains its own club committee and staff and operates several youth teams as well as amateur side Basconia B who compete in the Preferente de Vizcaya league, two levels below the first team. These other teams play in a separate small stadium in the town, Soloarte. Occasionally the main squad has been supplemented by some of Basconia's 'own' players in emergencies – Mikel Rico was with Basconia B when he appeared in one Tercera División fixture in 2001; he left Biscay for a long career across Spain which eventually brought him back to sign for Athletic in 2013.

In January 2018, with the team struggling to remain in the league, Basconia took the unusual step of recruiting some older, more experienced players including Thaylor Lubanzadio to help them maintain their 23-year divisional status, which was eventually accomplished – they finished 15th, 5 points above the relegation zone.