The 1980–81 Segunda División B was the 4th season of Segunda División B, the third highest level of the Spanish football league system, since its establishment in 1977.
A total of 20 teams will contest the group, including 2 relegated from the Segunda División and 4 promoted from the Tercera División.
Teams relegated from 1979–80 Segunda División Teams promoted from 1979–80 Tercera División Teams from Aragon, Asturias, Basque Country, Canary Islands, Castile and León, Galicia, La Rioja and Madrid.
A total of 20 teams will contest the group, including 2 relegated from the Segunda División and 4 promoted from the Tercera División.
Teams relegated from 1979–80 Segunda División Teams promoted from 1979–80 Tercera División Teams from Andalusia, Andorra, Balearic Islands, Castilla–La Mancha, Catalonia, Extremadura, Region of Murcia and Valencian Community.