This study introduces one specimen each of the genera Gymnopilus, Marasmius, and Mycena as an unrecorded species found in the Hwasun Gotjawal and Jeju Gotjawal Provincial Park of the Hangyeong-Andeok terrain, South Korea. Morphological analyses of macroscopic and microscopic features, and molecular analysis of the nuclear ribosomal internal transcribed spacer region were conducted to identify the specimens. Our results indicated that the newly identified specimens were Gymnopilus dilepis, Marasmius tenuissimus, and Mycena seminau. Here, we describe these newly identified mushroom species and provide baseline data on their diversity in Gotjawal, South Korea.