Korean fir (Abies koreana), an endangered alpine conifer native to Korea, has recently experienced severe dieback on Mount Deogyu owing to climate change–induced thermal and water stress. As rhizosphere microbial communities play a vital role in tree health and stress resistance, this study aimed to isolate and identify previously unrecorded fungal species from the rhizosphere of A. koreana. Soil samples were collected from natural stands on Mt. Deogyu, and fungi were isolated using the dilution plating method on Potato Dextrose Agar medium. The isolates were identified based on morphological characteristics and phylogenetic analyses of internal transcribed spacer regions and large-subunit ribosomal DNA sequences. Three fungal species—Mucor fusiformisporus, Mortierella turficola, and Entomortierella sugadairana—were identified for the first time in Korea. These species are saprotrophic members of Mucoromycota and Mortierellomycota, which participate in organic matter decomposition, phosphorus solubilization, and nutrient cycling in cold forest soils. Members of the Mortierellaceae family are plant growth–promoting fungi that maintain high enzymatic activity in subalpine environments, contributing to nutrient availability through mechanisms such as phosphate solubilization and siderophore production. This study provides baseline taxonomic information on the fungal diversity associated with A. koreana. Furthermore, the identification of cold-adapted and phosphorus-solubilizing fungi suggests their potential as valuable microbial resources for future conservation and restoration strategies for this endangered species.