Instant mashed potatoes are potatoes that have been through an industrial process of cooking, mashing and dehydrating to yield a packaged convenience food that can be reconstituted by adding hot water or milk, producing an approximation of mashed potatoes. They are available in many different flavors.

Mashed potatoes can be reconstituted from potato flour, but the process is made more difficult by lumping; a key characteristic of instant mashed potatoes is that it is in the form of flakes or granules, eliminating the chunkiness. Analogous to instant mashed potatoes are instant poi made from taro and instant fufu made from yams or yam substitutes including cereals. Poha, an instant rice mush, is also much in the same spirit, as more broadly are other instant porridges, formed from flakes, granules, or pearls to avoid lumping. Brands include Smash and Idahoan Foods.

Flaked instant mashed potatoes are most commonly found in stores in the United States and Canada. Granulated forms are generally reserved more for institutional or restaurant use.

The practice of drying and grinding starchy root vegetables for preservation and portability is widely attested around the world, and likely dates back to before the advent of agriculture. Potatoes in particular have been freeze dried since at least the time of the Inca empire, in the form of chuño; another example is in Japanese Ainu cuisine, where potatoes are collected frozen from the ground in spring, then dried.

U.S. Patent 1,025,373, developed by Mr. Sullivan, titled "Dehydrate Potatoes and Process of Preparing the Same", and describing a product that was to be reconstituted in hot water, was applied for in 1905 and granted in 1912.

Flake-form instant mashed potatoes date back at least to 1954, when two United States Department of Agriculture researchers were issued a patent for "Drum drying of cooked mashed potatoes" (U.S. Patent 2,759,832), which describes the end product specifically being "as a thin sheet or flake".

In 1962, Canadian scientist Edward A. Asselbergs was issued U.S. Patent 3,260,607, entitled "Preparation of dehydrated cooked mashed potato", for a particular industrial method of producing the product.