2017–18 Tercera División

The 2017–18 Tercera División will be the fourth tier in Spanish football. It will begin play on August, 2017 and will end in late June 2018 with the promotion play-off finals.

Competition format

 * 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.