|Full name||Alexander Quintanilla Urionabarrenetxea|
|Date of birth||2 July 1990|
|Place of birth||Bilbao, Spain|
|Height||1.83 m (6 ft 0 in)|
|Playing position(s)||Centre back|
|2008–2009||→ Danok Bat (loan)|
|2009–2010||→ Portugalete (loan)||32||(0)|
|* Senior club appearances and goals counted for the domestic league only and correct as of 8 March 2020|
Born in Bilbao, Biscay, Quintanilla finished his graduation with Danok Bat CF, on loan from Athletic Bilbao. In the 2009 summer he was loaned to Club Portugalete in Tercera División, making his senior debut for the club during the campaign.
In June 2010 Quintanilla returned to Athletic, being assigned to the reserves in Segunda División B. On 19 July 2011, after featuring regularly, he signed a one-year deal with fellow league team Deportivo Alavés.
On 10 July 2012 Quintanilla signed for another reserve team, Valencia CF Mestalla also in the third tier. He was called up to the first team by manager Mauricio Pellegrino for the pre-season, and was also an unused substitute in a 2–0 Copa del Rey away win against CA Osasuna on 11 December.
On 29 January 2014, Quintanilla signed a six-month contract with Barakaldo CF. He was an undisputed starter for the club during the following two seasons, contributing with three goals in 36 appearances in 2015–16.
On 22 July 2016, Quintanilla signed a two-year deal with Segunda División club UD Almería. He made his professional debut on 6 September, starting in a 0–2 Copa del Rey home loss against Rayo Vallecano.
Quintanilla's debut in the second level came on 21 September 2016, as he started and was sent off in a 0–4 away loss against UCAM Murcia CF. On 10 January 2017 he rescinded his contract, and moved to fellow league team CD Mirandés the following day.
Quintanilla returned to the Andalusians in June 2017, but still terminated his contract on 1 September. The following 31 January, he signed a two-and-a-half-year contract with Córdoba CF, still in the second division.
On 27 June 2019, after suffering relegation, Quintanilla left the Blanquiverdes after terminating his contract, and signed for third tier side UD Ibiza on 28 August. On 21 September 2020, he signed a one-year contract with Gimnàstic de Tarragona also in division three.
- "Álex Quintanilla vuelve al Bilbao Atletic [sic]" [Álex Quintanilla returns to Bilbao Atletic] (in Spanish). El Correo. 24 June 2010. Retrieved 24 July 2016.
- "Sendoa, Azkorra, Quintanilla y Nájera, nuevos jugadores del Deportivo Alavés" [Sendoa, Azkorra, Quintanilla and Nájera, new players of Deportivo Alavés] (in Spanish). El Mundo. 19 July 2011. Retrieved 24 July 2016.
- "Quintanilla firma por tres años" [Quintanilla signs for three years] (in Spanish). Super Deporte. 10 July 2012. Retrieved 24 July 2016.
- "El canterano de la semana: Alex Quintanilla, un central de Lezama para el Valencia" [The youth player of the week: Alex Quintanilla, a Lezama stopper to Valencia] (in Spanish). Goal.com. 23 July 2012. Retrieved 24 July 2016.
- "Se repite la historia en el Reyno" [The history repeats itself at the Reyno] (in Spanish). Marca. 11 December 2012. Retrieved 24 July 2016.
- "Álex Quintanilla ficha por el Barakaldo C.F." [Álex Quintanilla signs for Barakaldo C.F.] (in Spanish). Barakaldo CF. 29 January 2014. Retrieved 24 July 2016.
- "El Almería ficha al centrocampista Diamanka y al central Alex Quintanilla" [Almería sign central midfielder Diamanka and stopper Alex Quintanilla] (in Spanish). UD Almería. 22 July 2016. Retrieved 24 July 2016.
- "El Rayo se toma su venganza y elimina al Almería" [Rayo take their vengeance and knock out Almería] (in Spanish). Marca. 7 September 2016. Retrieved 7 September 2016.
- "El Almería y Alex Quintanilla llegan a un acuerdo para rescindir el contrato" [Almería and Alex Quintanilla reach an agreement to rescind the contract] (in Spanish). UD Almería. 10 January 2017. Retrieved 11 January 2017.
- "Alex Quintanilla, nuevo jugador del Club Deportivo Mirandés" [Alex Quintanilla, new player of Club Deportivo Mirandés] (in Spanish). CD Mirandés. 11 January 2017. Retrieved 14 January 2017.
- "Alex Quintanilla y Antonio Marín dejan de pertenecer a la UD Almería" [Alex Quintanilla and Antonio Marín leave UD Almería] (in Spanish). UD Almería. 1 September 2017. Retrieved 1 September 2017.
- "Alex Quintanilla, nuevo fichaje del Córdoba Club de Fútbol" [Alex Quintanilla, new signing of Córdoba Club de Fútbol] (in Spanish). Córdoba CF. 31 January 2018. Retrieved 2 February 2018.
- "Quintanilla deja de pertenecer al Córdoba CF" [Quintanilla leaves Córdoba CF] (in Spanish). Córdoba CF. 27 June 2019. Retrieved 27 June 2019.
- "Ibiza signs Álex Quintanilla". UD Ibiza. 28 August 2019. Retrieved 21 September 2020.
- "Alex Quintanilla vestirà de grana" [Alex Quintanilla will wear grana] (in Catalan). Gimnàstic Tarragona. 21 September 2020. Retrieved 21 September 2020.
- "Yo jugué en el Real Betis: Txirri" [I played at Real Betis: Txirri] (in Spanish). Vavel. 14 January 2014. Retrieved 24 July 2016.