A milk substitute is any substance that resembles milk and can be used in the same ways as milk. Such substances may be variously known as non-dairy beverage, nut milk, grain milk, legume milk, mock milk and alternative milk.

Infant formula, also called baby formula, simply formula, baby milk or infant milk, is an ultra-processed food designed and marketed for feeding to babies and infants under 12 months of age, usually prepared for bottle-feeding or cup-feeding from powder or liquid. The U.S. Federal Food, Drug, and Cosmetic Act (FFDCA) defines infant formula as "a food which purports to be or is represented for special dietary use solely as a food for infants by reason of its simulation of human milk or its suitability as a complete or partial substitute for human milk".