A wine cellar is a storage room for wine in bottles or barrels, or more rarely in carboys, amphorae or plastic containers. In an active wine cellar, important factors such as temperature and humidity are maintained by a climate control system. In contrast, passive wine cellars are not climate-controlled, and are usually built underground to reduce temperature swings. An aboveground wine cellar is often called a wine room, while a small wine cellar (less than 500 bottles) is sometimes termed a wine closet.

Wine cellars protect alcoholic beverages from potentially harmful external influences, providing darkness and a constant temperature. Wine is a natural, perishable food product. Left exposed to heat, light, vibration or fluctuations in temperature and humidity, all types of wine can spoil. When properly stored, wines not only maintain their quality but many actually improve in aroma, flavor, and complexity as they mature.

Wine can be stored satisfactorily between 7–18 °C (45–64 °F) as long as any variations are gradual. A temperature of 13 °C (55 °F), much like what is found in the caves used to store wine in France, is ideal for both short-term storage and long-term aging of wine. Note that wine generally matures differently and more slowly at a lower temperature than it does at a higher temperature. When the temperature swings are significant, 14 degrees or more, it will cause the wine to breathe through the cork which significantly speeds up the aging process. Between 10–14 °C (50–57 °F), wines will age normally.