[4] The Tercera Federación features 18 regional groups (like the former fourth tier Tercera División), corresponding to the autonomous communities of Spain (due to its size, Andalusia is divided into two groups, East and West; Ceuta is allocated to West Andalusia, while Melilla is allocated to the East), where each group is administered by a regional football federation.

At the end of the season the first four teams in each group qualify for promotion play-offs to decide which teams are promoted to Segunda Federación.

At least the three teams finishing bottom of each group may be relegated to the Divisiones Regionales de Fútbol.

The eighteen group champions also qualify for the following season's Copa del Rey.

The member clubs of the Tercera Federación for the 2024–25 season are listed below.