Burl is a tree growth in which the grain has grown in a deformed manner. It is commonly found in the form of a rounded outgrowth on a tree trunk or branch that is filled with small knots from dormant buds.

Burls yield a very peculiar and highly figured wood, one prized for its beauty by many; its rarity also adds to its expense. It is sought after by people such as furniture makers, artists, and wood sculptors.

It's used in turnings for fine pens, furniture and bowls. There are a number of well-known types of burls (each from a particular species); these are highly valued and used as veneers in fine furniture.