The cantera (quarry) of Spanish professional football club Athletic Bilbao is the organisation's youth academy, developing players from childhood through to the integration of the best prospects into the adult teams.
 The final category within the youth structure is the Juvenil A (Basque: Gazteak A) under-18/19 team which represents the club in national competition. The successful graduates then usually move to the club's affiliated team for younger players, CD Basconia, or occasionally directly to the reserve team, Bilbao Athletic, both of which are also considered part of the cantera due to being stages in progression towards the senior team, albeit competing in the adult league system.
 The academy is based at the club training complex, Lezama, which is often the metonym used to refer to the system itself.
 The top football clubs in the Spanish leagues generally place great importance in developing their cantera to promote the players from within or sell to other clubs as a source of revenue. As a club who have a small pool of players to choose from due to their Basque-only policy, this focus on home-grown talent is even more vital to Athletic Bilbao.
 Most of the senior team players in recent seasons are youth academy graduates: 15 of the squad in 2014 (as per analysis from the CIES Football Observatory). In 2016, Athletic's total of 17 'homegrown players' (as per UEFA guidelines: three years of training between 15 and 21 years old) still at their formative club was the highest across Europe's 'big five' leagues, significantly more than all other elite clubs apart from neighbours Real Sociedad. Including eight former trainees at other eligible clubs, Athletic's total of 25 homegrown players ranked as the fifth-highest across the continent, although only third in Spain behind Real Madrid and FC Barcelona who retained just a few of the many high-level professionals they produced. Moreover, further end-of-year analysis demonstrated that these graduates were not merely backup squad members but integral elements of the team, involved  in 64% of the minutes in the 2016–17 La Liga, where they finished 7th.
 The core of boys from the local Biscay province are first introduced into the Lezama Alevín teams at around 10 years of age and advance by an age group every season through Infantil, Cadete and Juvenil levels; there are collaboration agreements in place with the small clubs in the province, whose staff collaborate with Athletic scouts to identify any standout talents emerging at each stage. The players who are retained by Athletic after their Juvenil A spell (aged about 18) typically join the club's farm team in Basauri, CD Basconia, playing at the regionalised fourth level of the Spanish adult system. Their squad is normally expanded further with new signings from the wider regions's youth clubs, most notably Danok Bat and Antiguoko who regularly challenge the professional academy teams for the title in their División de Honor group. A number of senior players have also emerged from the Txantrea club in Pamplona who have a collaborative agreement with Athletic (renewed for four more years in 2017).
 The players usually spend one or two seasons at Basconia, some going out on loan to other local clubs, before the best are promoted to the reserve team Bilbao Athletic and then on to the senior team when considered ready to do so. There are exceptions to this sequence; notably Iker Muniain showed such promise that he was promoted early to Juvenil A as a 15-year-old in 2008, was selected by Bilbao Athletic as soon as he turned 16 in January 2009 and became a senior team regular at the start of the next season.
 The club received its first large transfer windfall for a player who had graduated from the youth system since the €12 million deal of summer 2005 which took Asier del Horno to Chelsea in January 2018, when Aymeric Laporte (one of the few French players to have played for the club at any level) moved to Manchester City for a fee of around €64 million, his contractual release clause amount. That deal was eclipsed seven months later when goalkeeper Kepa Arrizabalaga, an Athletic player since the age of 9, was acquired by Chelsea for his release clause of €80 million, making him the world's most expensive goalkeeper. 
 The Juvenil A team play in Group II of the División de Honor Juvenil de Fútbol as their regular annual competition. Their main rivals in the league group are Real Sociedad and Osasuna. The under-17 team, Juvenil B, plays in the Liga Nacional Juvenil which is the lower division of the same structure.
 The team also regularly participates in the Copa de Campeones Juvenil and the Copa del Rey Juvenil, qualification for which is dependent on final league group position.  In these nationwide competitions the opposition includes the academy teams of Barcelona, Atlético Madrid, Sevilla and Real Madrid.
 For many years Athletic have been active in entering their youth team into international tournaments to gain experience, and in recent times these events have gained prominence in the football calendar. In 2012 the Juvenil team (including Aymeric Laporte and Iñaki Williams) appeared in the invitational NextGen Series but this was subsequently discontinued.
 In 2013-14 Athletic's senior team qualified for the Champions League group stages, meaning that the Juvenil squad could play in the 2014-15 version of the UEFA Youth League. In the subsequent years there was no further chance to participate in that competition due to the senior team failing to qualify.  The alternative route into the Youth League would be to win the previous season's Copa de Campeones but Athletic Juvenil have so far been unable to achieve this – they were losing finalists in 2022.
 A younger age group (The Cadete B squad) also competes in the Manchester United Premier Cup annually. In 1998 Athletic, coached by future senior team boss Ernesto Valverde, won the tournament, although none of the players involved – not even Player Of The Tournament Jonan García – were able to become regulars in the senior team. Coincidentally that season was also very successful for other sections within the club: the senior team finished 2nd in the league and qualified for the Champions League while Bilbao Athletic finished 2nd in their Segunda B group and Basconia won their Tercera section, although neither subsidiary was promoted.
 In 2006 (featuring Erik Morán in the squad) and 2012 (including Asier Villalibre) Athletic cadets also competed at the Manchester United Premier Cup world finals as the Spanish league representative after winning the national qualifier.
 The coaches are often former Athletic players who themselves graduated from Lezama. The directors of the academy, Rafael Alkorta and Andoni Ayarza, are also former players, as was their predecessor José María Amorrortu, and the president he worked under, Josu Urrutia.
 Note: Flags indicate national team as defined under FIFA eligibility rules. Players may hold more than one non-FIFA nationality.
 Notable graduates who passed through the youth system on their way to establishing themselves with the Athletic senior side and/or other clubs (since the opening of Lezama in 1971) include:
 players currently at Athletic in bold, 'graduation' year in parentheses
  
 Double-winning seasons shown in bold 
 Seasons with two or more trophies shown in bold
 National competitions