Cystoseira squarrosa (Fucophyceae, Fucales), a rare Mediterranean endemic, is reported for the first time from Spanish coastal waters (Fenals, Lloret de Mar, Girona), where it was growing on a rocky substratum at 8 m depth. This is now the only known locality of C. squarrosa in the North-Western Mediterranean, after its almost sure extinction at the sites from where it was described in the 1840’s (Nice, Genova).