Usnea Adans. is a somewhat rare lichen in South Korea, and, in nearly two decades, no detailed taxonomic or revisionary study has been conducted. This study was based on the specimens deposited in the lichen herbarium at the Korean Lichen Research Institute, and the samples were identified using information obtained from recent literature. In this study, a total of eight species of Usnea, including one new record, Usnea hakonensis Asahina, are documented. Detailed descriptions of each species with their morphological, anatomical, and chemical characteristics are provided. A key to all known Usnea species in South Korea is also presented.