The investigation of Agaricales diversity in the Antarctica is limited, with only seven genera reported for the region. Galerina stands out as the genus with the highest species diversity, including 12 species in Antarctica. This research reports the presence of G. marginata in the region, providing the first complete morphological description for the specimen developing in Antarctica. Sampling was conducted during the Austral summer of 2022/2023 as part of the XLI Brazilian Antarctic Operation in Point Smellie, Byers Peninsula, Livingston Island, South Shetland Archipelago, Antarctica. Phylogenetic relationships reconstructed by Maximum Likelihood demonstrate that G. marginata forms a monophyletic clade with over 60% bootstrap support in most branches. The isolate in this study was found to be internal to the main cluster. Evolutionary reconstructions using the Maximum Likelihood method indicate that the branches correspond to the Antarctic isolate being an internal clade within the marginata group. Recording fungal populations in polar regions offers information about their adaptation and survival in inhospitable environments. Understanding the species' distribution in Antarctica encourages future investigations into its ecology and interactions with other organisms. Here, data are presented to establish an initial foundation for monitoring the G. marginata population in Antarctica and assessing the potential impacts of climate change on its development and survival in the forthcoming years. We report the third occurrence of Galerina marginata (Batsch) Kühner in Antarctica and provide, for the first time, a comprehensive morphological description of an individual of the species for the Antarctic continent, accompanied by phylogenetic analyses and comprehensive discussions regarding its diversity and global distribution.