Bubbles in carbonated water float to the surface.

Carbonated water, also known as soda water, sparkling water, or seltzer water, is water containing carbon dioxide, which bubbles out when the drink is depressurised. When bottled or supplied for final consumption without flavoring, it may be called club soda.

Historically, the first soda waters were prepared by adding sodium bicarbonate to lemonade. A chemical reaction between sodium bicarbonate and citric acid creates carbon dioxide.

Swedish chemistry professor Torbern Bergman succeeded in making carbonated water in 1771, mostly to save himself money when he was ill. He was trying to imitate the naturally-occurring effervescent water that bubbles up from underground springs and was thought to be beneficial to health.

Currently, carbonated water is made by passing pressurized carbon dioxide through water. This increases the solubility; i.e., more carbon dioxide dissolves than under standard atmospheric pressures. When the pressure is reduced by opening the bottle, the gas comes out of the solution, forming the characteristic bubbles.

Carbonated water is believed by some to be good for removing stains, for example coffee stains from mugs, or stains from silver. A frequently used method of preventing red wine stains from setting in is to sprinkle salt on the stain and then apply a liberal amount of carbonated water. Schweppes manufactures unflavoured "soda water", adding to it sodium bicarbonate, thus acting as a weak antacid.

The most popular forms are flavored, and referred to as soft drinks. These are widely sold throughout the world. Major brands include Coca-Cola, Pepsi, R.C. Cola, and Dr Pepper. Many sales of these beverages are made via vending machines.