Tercera División is the fourth level of the Spanish football league system. The top three are the Primera División, often referred to as "La Liga" in English, the Segunda División, and Segunda División B.
Since 2006, the Tercera División features 360 teams divided into 18 regional groups, corresponding to the Autonomous communities of Spain (due to its huge size, Andalusia is divided into two different groups, East and West; Ceuta is allocated to West Andalusia, while Melilla is allocated to the East). 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 División B. At least the three teams finishing bottom of each group may be relegated to the Divisiones Regionales de Fútbol. However the number of teams relegated can vary. The eighteen group champions also qualify for the following season's Copa del Rey. However reserve teams are ineligible. Along with teams from Segunda División B, the remaining teams from the division compete in the Copa Federación.
Since the 2008–09 season, the eighteen group winners have the opportunity to promote directly to the Segunda División B. The 18 group winners are drawn into a two-legged series where the nine winners promote to the Segunda División B. The nine losing clubs enter the playoff round for the last nine promotion spots.
The 18 runners-up are drawn against one of the seventeen fourth-place clubs outside their group and the 18 third-placed clubs are drawn against one another in a two-legged series. The twenty-seven winners advance with the nine losing clubs from the champions' series to determine the 18 teams that enter the last two-legged series for the last nine promotion spots. In all the playoff series, the lower-ranked club plays at home first. Whenever there is a tie in position (like the group winners in the champions' series or the third-placed teams in the first round), a draw determines the club to play at home first.
- The top four eligible teams in each group will play the promotion playoffs.
- The champion of each group will qualify to 2018–19 Copa del Rey. If the champion is a reserve team, the first non-reserve team qualified will join the Copa.
- In each group, at least three teams will be relegated to Regional Divisions.
These area the 18 champions:
Group I: Compostela.Group II: Real Oviedo B.
Group III: Gimnástica de Torrelavega.
Group IV: SCD Durango.
Group V: Espanyol B.
Group VI: Atlético Levante.
Group VII: SADCF Internacional DSL.
Group VIII: Unionistas de Salamanca.
Group IX: Atlético Malagueño.
Group XI: Mallorca B.
Group X: Cadiz B
Group XII: Tenerife B.
Group XIII: Yeclano Deportivo.
Group XIV: Don Benito.
Group XV: Mutilvera.
Group XVI: Calahorra.
Group XVII: Teruel.
Group XVIII: Conquense
Play Off (Champions)
Cultural Durango - Group 4
Inter - Group VII
Unionistas Salamanca- Group VIII
Cadiz B- Group X
Group XI: Mallorca B.
Don Beniyo- Group XIV
Inter - Group VII
Unionistas Salamanca- Group VIII
Cadiz B- Group X
Group XI: Mallorca B.
Don Beniyo- Group XIV
Play Offs