The 2017–18 División de Honor was the 51st season of the top flight of the Spanish domestic rugby union competition since its inception in 1953.

Valladolid won its second consecutive title, its eighth overall after defeating local arch-rivals SilverStorm El Salvador in the Final.

The División de Honor season takes place between September and March, with every team playing each other home and away for a total of 22 matches.

The relegation playoff was played over two legs by Hernani, the team finishing 11th in División de Honor and Ciencias Sevilla, the losing team from División de Honor B promotion playoff final.

Hernani won 57-48 on aggregate and remained in the División de Honor A.