Abstract The chemical composition of the essential oil of spontaneous Rosmarinus officinalis from Greece was analyzed by GC and GC/MS and tested for its antifungal activity against five phytopathogenic fungi (Sclerotinia sclerotiorum, Phytophthora nicotianae, Sclerotium cepivorum, Fusarium oxysporum f. sp. dianthi and Fusarium proliferatum). Thirty-seven components compounds representing 97.3% of the total oil were identified. The major constituents were Î±-pinene (24.1%), camphor (14.9%), 1,8-cineole (9.3%), camphene (8.9%), Î±-terpineol (8.8%) and borneol (8.0%). The most sensitive fungus was Ph. nicotianae, followed by S. sclerotiorum, S. cepivorum, F. proliferatum and F. oxysporum f. sp. dianthi.