The 2020–21 season marked Athletic Bilbao's 122nd year in existence and their 90th consecutive campaign in Spain's top flight, as they competed in La Liga, the Copa del Rey, and the Supercopa de España. The season ran from 20 July 2020 to 30 June 2021, with a delayed start and compressed schedule caused by the COVID-19 pandemic in Spain. Notably, this was the club's first season since 2011–12 without legendary striker Aritz Aduriz, who retired in May 2020. The league fixtures were announced on 31 August 2020, while the Supercopa draw took place on 17 December 2020. Interestingly, the official statistics for this season do not include the postponed 2020 Copa del Rey Final, which was delayed until April 2021 and counted under the 2019–20 season's records in some resources. Despite the disruptions, the squad—featuring both first-team players and reserve team members—worked through transfers and friendlies to navigate this unusual campaign.