Silage () is a type of fodder made from green foliage crops which have been preserved by acidification, achieved through fermentation. It can be fed to cattle, sheep and other such ruminants (cud-chewing animals). The fermentation and storage process is called ensilage, ensiling or silaging, and is usually made from grass crops, including maize, sorghum or other cereals, using the entire green plant (not just the grain). Silage can be made from many field crops, and special terms may be used depending on type: oatlage for oats, haylage for alfalfa (haylage may also refer to high dry matter silage made from hay).

Silage can be made by one or more of the following methods: placing cut green vegetation in a silo or pit; piling the vegetation in a large heap and compressing it down so as to purge as much oxygen as possible, then covering it with a plastic sheet; or by wrapping large round bales tightly in plastic film.