Moisture generally refers to the presence of water, often in trace amounts.

The moisture content is often an important aspect of various foodstuffs including cheese and many dried goods such as tea where excess moisture can promote bacterial growth, decay, molding, or rotting over time.

Excessive moisture is usually undesirable and can also cause rot in wood or other organic material, corrosion in metals, and electrical short circuits. Many home and business owners go to great pains to prevent these effects. Many products are sold to prevent this. Some foodstuffs and other packaged products come with desiccators, often made of silicon oxide, to absorb moisture.

In skin, leather, and wood, moisture can also refer to natural oils.

Moisture is also sometimes used to refer to the liquid form of solvents other than water, especially when present in a solid.