Nixtamalization typically refers to a process for the preparation of maize (corn), or other grain, in which the grain is soaked and cooked in an alkaline solution, usually limewater, and hulled. The term can also refer to the removal via an alkali process of the pericarp from other grains such as sorghum. Maize subjected to the nixtamalization process has several benefits over unprocessed grain for food preparation: it is more easily ground; its nutritional value is increased; flavor and aroma are improved; and mycotoxins are reduced. These benefits make nixtamalization a crucial preliminary step for further processing of maize into food products, and the process is employed using both traditional and industrial methods, in the production of tortillas, tamales, corn chips, hominy and many other items.

In the Aztec language Nahuatl, the word for the product of this procedure is nixtamalli or nextamalli (pronounced [niʃtaˈmalːi] or [neʃtaˈmalːi]), which in turn has yielded Mexican Spanish nixtamal ([nistaˈmal]). The Nahuatl word is a compound of nextli "ashes" and tamalli "unformed corn dough, tamal." The term nixtamalization (spelled with the "t") can also be used to describe the removal of the pericarp from any grain by an alkali process, including maize, sorghum, and others. When the unaltered Spanish spelling nixtamalización is used in written English, however, it almost exclusively refers to maize.