Former La Liga sides Real Oviedo and Gimnastic have been promoted to La Segunda after triumphing in the third-tier playoffs on Sunday.
Both clubs finished top of their respective groups in Segunda B and qualified for the champions’ playoffs, along with Cadiz and Huesca.
Oviedo defeated Cadiz 2-1 over two legs, while Nastic ran out 3-1 winners in the second leg of their tie with Huesca.
Traditionally a modest La Liga club, Los Azules return to La Segunda for the first time in 12 years, having been beset by financial troubles since their relegation from the top flight in 2001.
However, Carlos Slim, the world’s richest man, ensured the club survived extinction by raising a necessary €2.5m in November 2012, while they ended a successful share sale to the general public on May 29.
Nastic, meanwhile, were last a Primera club in 2007 and have spent subsequent seasons struggling in the bottom two tiers.