A muffin mix is a premixed, shelf-stable blend of dry ingredients, usually flour, sugar, baking powder, and salt, sold so that home cooks only need to add wet ingredients like milk, oil, or eggs before baking.
Commercial muffin and baking mixes date to the 1930s in the United States, with brands such as Jiffy and Bisquick among the earliest to popularize them; muffin-specific mixes in flavors like blueberry, chocolate chip, corn, and bran followed as the category grew through the mid-20th century.
Muffin mix trades some flavor depth and texture for speed and consistency compared with a from-scratch batter, but it can be customized by folding in extras such as fresh or dried fruit, nuts, or chocolate chips before baking.