A duster is a light, loose-fitting long coat. The original dusters were full-length, light-colored canvas or linen coats worn by horsemen to protect their clothing from trail dust. These dusters were typically slit up the back to hip level for ease of wear on horseback. Dusters intended for riding may have features such as a buttonable rear slit and leg straps to hold the flaps in place. For better protection against rain, dusters were made from oilcloth and later from waxed cotton.

In the late 19th and early 20th centuries, both men and women wore dusters to protect their clothes when riding in open motorcars on the dirt roads of the day.