In many places, "mineral water" is often colloquially used to mean carbonated water (which is usually carbonated mineral water, as opposed to tap water).

Mineral water is water containing minerals or other dissolved substances that alter its taste or give it therapeutic value. Salts, sulfur compounds, and gases are among the substances that can be dissolved in the water. Mineral water can often be effervescent. Mineral water can be prepared or can occur naturally.

Traditionally mineral waters would be used or consumed at their source, often referred to as taking the waters or taking the cure, and such sites were referred to as spas, baths or wells. Spa would be used when the water was consumed and bathed in, bath when the water was not generally consumed, and well when the water was not generally bathed in. Often an active tourist centre would grow up around a mineral water site (even in ancient times; see Bath). Such tourist development resulted in spa towns and hydropathic hotels (often shortened to Hydros).

In modern times, it is far more common for mineral waters to be bottled at source for distributed consumption. Travelling to the mineral water site for direct access to the water is now uncommon, and in many cases not possible (because of exclusive commercial ownership rights). There are over 3000 brands of mineral water commercially available worldwide.

The U.S. FDA classifies mineral water as water containing at least 250 parts per million total dissolved solids (TDS), and is also water coming from a source tapped at one or more bore holes or spring, originating from a geologically and physically protected underground water source. No minerals may be added to this water.