In chemistry, disaccharides are carbohydrates consisting of two monosaccharide units.

The units are joined via a condensation reaction.

Like monosaccharides, they tend to be tasty, water soluble, and crystalline. A number occur in nature. The most common are sucrose("table" or cane sugar), lactose (milk sugar) and maltose found in malted Barley to some extent. Trehalose is present in some fungi, and there has been some success at industrial production for use as an ingredient.

Maltose and Cellobiose are hydrolysis products of the polysaccharides starch and cellulose respectively.