The order Hypocreales, which belongs to the Ascomycota class Sordariomycetes, has a large number of species and occupies a variety of ecological niches, including saprophytic, symbiotic, and parasitic fungi. While much research has focused on terrestrial Hypocrealean fungi, there remains a significant gap in our understanding of their diversity and ecological roles in marine environments. In this study, we isolated 47 fungal strains from various marine habitats in South Korea. Through the polyphasic study, including phylogenetic analysis using multi-genetic markers (ITS, LSU, TEF1, RPB2, TUB, and ACT) and morphological analysis, we identified 21 species previously undiscovered in Korea, including 5 new and 16 unrecorded species. Our findings illustrate the species diversity of marine Hypocreales, highlighting the need for additional research into their ecological functions and potential in biotechnology and medicine.