A doughnut made with potato flour or potato starch as a main ingredient is called a Spudnut.
Spudnuts are a form of potato doughnut. Depending on the recipe, the potato component may be potato flour, potato starch, or mashed potato, replacing much of the wheat flour used in ordinary doughnuts. The result is often described as lighter, softer, or fluffier than a conventional flour-based doughnut.
The name became especially well known through Spudnut Shops, an American chain founded by brothers Al and Bob Pelton. After tasting potato-based doughnuts in Germany, the brothers developed a dry potato mix and began selling the product in Salt Lake City around 1940. The concept spread rapidly through franchising.
At its height in the mid-20th century, the chain had hundreds of locations across the United States. The original company eventually disappeared, but independent shops and recipes remain. “Spudnut” is therefore both a general name associated with potato doughnuts and a historically important commercial brand.