The present article provides a comprehensive review of Jeju lava seawater (JLS), a unique underground water resource from Jeju Island, Korea, renowned for its distinct mineral composition. Herein, its biological effects and potential underlying mechanism(s) of action are summarized, with a particular focus on the pivotal roles of its mineral components. Many studies have indicated that JLS possesses potent antioxidant, anti-inflammatory, and antimelanogenic properties, along with beneficial effects on metabolic disorders, skin health, and joint conditions. These diverse effects are attributed to its rich profile of macro-minerals (e.g., magnesium, calcium, potassium) and trace elements (e.g., zinc, selenium, vanadium, germanium), which synergistically modulate key cellular pathways, including nuclear factor erythroid 2-related factor 2, mitogen-activated protein kinases, nuclear factor kappa-light-chain-enhancer of activated B cells, and adenosine monophosphate-activated protein kinase. Current applications include cosmetics, functional foods, and balneotherapy, supported by robust safety data from genotoxicity and oral toxicity studies. Although preclinical evidence is compelling, further large-scale human clinical trials are essential to fully establish its therapeutic potential and optimize its application across various health domains.