2021 Tercera División play-offs
The 2021 Tercera División play-offs to Segunda División RFEF from Tercera División (promotion play-offs) will be the final play-offs for the promotion from 2020–21 Tercera División to 2021–22 Segunda División RFEF. The last four teams from the promotion groups and the top two clubs from the Play-off groups will qualify for this stage. Format. Due to the health crisis caused by the COVID-19 pandemic in Spain, the RFEF decided for this season that there would be no games between teams from different Territorial Federations and thus not have problems with mobility  restrictions. In addition, the remodeling of the RFEF national categories allows each Third Division group to have three promotion slots to the new Segunda División RFEF category, one of them through promotion play-offs. Six teams qualify from each of the Third Division groups. Four of them come from the groups called "C" or "promotion", and are those classified between the third and sixth position since the first two achieve direct promotion. The other two teams come from the groups called "D" or "play-off", and are the first two classified. As in the previous season, the promotion promotion is  a single match in which the highest ranked teams will have an advantage in the event of a tie. The fifth classified of group "C" will face the second classified of group "D"; and the sixth of the "C" will do the same with the first of the "D". The winners of this first round will face the third and fourth teams of group "C" in the final round, deciding the third place for promotion in each of the groups.