Down hairs, also called the ground hairs, are the very fine, fluffy hairs closest to the skin on some mammals. The hairs are short and crimped, which makes them highly efficient for trapping air and insulating the animal.

In the hobby of animal fancy, the down hair is collectively called the undercoat and is an important conformation point in shows, particularly dog and cat shows.

See also

• Awn hair
• Coat (animal)
• Fur
• Guard hair