Gouache (from the Italian guazzo, "water paint, splash") is a type of watercolor paint, made heavier and more opaque by the addition of a white pigment (chalk, Chinese white , etc.) in a gum arabic mixture. This results in a stronger color than ordinary watercolor.

The term was originally coined in the eighteenth century in France, although the technique is considerably older, having been in use as early as the sixteenth century in Europe.

The pigment dries slightly lighter than it appears when wet, which can make it difficult to match colors. The medium can also be susceptible to cracking if applied too thickly; this problem can be alleviated to some degree by the use of thickening media such as aquapasto. It can be very effective when applied to colored paper, for example in works by J.M.W. Turner.

Today the term gouache can be used interchangeably with body color , although the latter is made in a slightly different way. It can also be used as a term for any painting produced entirely with gouache.

Gouache was the original, and is still the primary, paint used in the production of decalcomanias.