Onsen in Japan are natural hot spring baths filled with mineral-rich water heated by volcanic activity. Unlike ordinary baths, onsen represent a unique cultural experience shaped by centuries of tradition, seasonal beauty, and etiquette. This beginner-friendly guide explains what an onsen is, how it differs from a public bath (sento), why hot springs became central to Japanese life, and what first-time visitors should know before entering. What Is an Onsen? An onsen is a natural hot spring bath defined by geothermal water that meets specific mineral and temperature standards under Japanese law. Under Japanese law, water qualifies as “onsen” ...
