The 2020–21 Segunda División season, also known as LaLiga SmartBank for sponsorship reasons, was the 90th since its establishment. The season began on 12 September 2020 and concluded on 31 May 2021. Teams Promotion and relegation (pre-season) A total of 22 teams contested the league, including 15 sides from the 2019–20 season, three relegated from the 2019–20 La Liga, and four promoted from the 2019–20 Segunda División B. This included the winners of the play-offs. Teams promoted to La Liga On 12 July 2020, Cádiz were the first team to be promoted to La Liga, ending a 14-year run in the lower divisions, seven of which were spent in Segunda División B, following Oviedo's 1−0 win against Zaragoza. The second team to earn promotion was Huesca after their 3−0 win against Numancia on 17 July 2020. This marks an immediate return to the first division. The final team to achieve promotion were play-off winners Elche after defeating Girona 1−0 on aggregate, they return to La Liga after a five-year absence, with one of those seasons spent in Segunda División B. Teams relegated from La Liga The first team to be relegated from La Liga were Espanyol. They were relegated on 8 July 2020, after a 1−0 loss against Barcelona in the Derbi Barceloní, after a 26-year stay in the top tier. The second team to be relegated were Mallorca, who were relegated on 16 July 2020 after a 1−2 home defeat against Granada, suffering an immediate return to the second division. The third and final relegated club were Leganés, after a 2−2 draw against Real Madrid on 19 July 2020, ending their four-year stay in La Liga. Teams relegated to Segunda División B The first team to be relegated from Segunda División were Racing Santander, after a 1−2 home loss against Elche on 4 July 2020, suffering an immediate return to the Segunda División B. The second team to be relegated were Extremadura, who were relegated on 4 July 2020 after trailing to Numancia 1−0 at home, ending a two-year stay in the second division. On 20 July 2020, the final round of the 2019–20 season, Numancia and Deportivo La Coruña were relegated after Albacete won 1–0 away to Cádiz. This ended Deportivo's 39-year streak in professional football, spending 25 of those years in La Liga, and also ended Numancia's 23-year stay in professional football, spending 4 of those years