During a survey of fungi on Araucaria araucana in Chile, a species of Ophiostoma morphologically different to O. araucariae was collected in the Andean region. Morphological characteristics and phylogenetic analyses of ITS, β-tubulin and EF-1α sequences confirmed that this species represents a novel taxon. This taxon is described here as Ophiostoma pehueninum sp. nov. The sexual morph of O. pehueninum was characterized by long neck and peridial hyphae around the bases, and allantoid ascospores surrounded by a gelatinous sheath. In culture a hyalorhinocladiella-like asexual morph was observed. Mating compatibility tests indicated that the species is heterothallic.