The 2025–26 Segunda Federación season is the fifth for the Segunda Federación, the fourth highest level in the Spanish football league system. Ninety teams participate, divided into five groups of eighteen clubs each based on geographical proximity. In each group, the champions are automatically promoted to Primera Federación, and the second to fifth placers will play promotion play-offs. The last five teams in each group are relegated to the Tercera Federación; in addition, the four worst teams classified 13th in their group play play-offs to define the last two relegation places.