The 2020–21 Campeonato de Portugal was the eighth season of Portuguese football's renovated third-tier league, since the merging of the Segunda Divisão and Terceira Divisão in 2013, and the sixth season under the current Campeonato de Portugal title.
Due to the cancellation of all non-professional competitions in the country due to the COVID-19 pandemic in Portugal on the previous season, no teams were relegated, which lead to an additional team from each of the 20 district championships.
The Portuguese Football Federation decided the creation of the Liga 3, a new tier in the Portuguese league system, beginning with the 2021–22 season, as well as a new format for Campeonato de Portugal, including the addition of four reserve teams invited from Primeira Liga clubs raising the total number of teams from 72 to 96.
In each series, teams played against each other in a home-and-away double round-robin system.
In the third stage, the best-placed teams of the two promotion series faced each other on a neutral venue to decide the champion.