<p>This study investigated the anatomy and histology of the olfactory organ of the Korean amur goby <i>Rhinogobius brunneus</i> from Jeonjucheon stream. This species lives in shallow, stagnant, and intermittently low-oxygenated streams, reservoirs, and ponds affected by seasonal rainfall. Anatomically, its olfactory organ consisted of a short tubular anterior nostril, a posterior nostril, a single longitudinal lamella, and two accessory nasal sacs (ethmoidal and lacrymal sacs). Its single lamella structure resembles other gobiid fishes with a simplified olfactory surface. Histologically, the sensory epithelium comprised olfactory receptor neurons, supporting cells, and basal cells, while the non-sensory epithelium contained stratified epithelial cells, basal cells, and mucous cells. In particular, the mucous cells stained intensely red with Hematoxylin and eosin and Masson’s trichrome, indicating proteinaceous granular mucins rich in glycoproteins; such secretions likely protect the epithelium against particles, toxins, and low-oxygenated freshwater. Overall, the goby’s olfactory organ exhibits traits uniquely adapted to stagnant and hypoxic conditions.</p>