明胶又称鱼胶或吉利丁（从英文名「Gelatine」译音而来），是一种从动物的骨头或结缔组织提炼出来，带浅黄色透明，无味的胶质，主要成分为蛋白质。

明胶通常用于食物、药物或化妆品的胶凝剂。明胶是胶原蛋白的一种不可逆的水解形式，且被归类为食品。它常用于软糖以及其他产品，如棉花糖、冰淇淋和优格。明胶一般用于食品的形式是片状，颗粒剂或粉末，有时使用时需在水中预溶。明胶其用于食品添加剂的E编码为E441。美国食品药物管理局（FDA）与欧洲食品安全局（EFSA）对于用牛骨制成的明胶是否会造成人类感染致命的狂牛病，认为风险很低但不是完全无风险。

Gelatin or gelatine (from Latin:gelatus meaning "stiff", "frozen"; compare with gelato) is a translucent, colorless, brittle (when dry), flavorless food derived from collagen obtained from various animal by-products. It is commonly used as a gelling agent in food, pharmaceuticals, photography, and cosmetic manufacturing. Substances containing gelatin or functioning in a similar way are called "gelatinous". Gelatin is an irreversibly hydrolyzed form of collagen, wherein the hydrolysis results in the reduction of protein fibrils into smaller peptides, which will have broad molecular weight ranges associated with physical and chemical methods of denaturation, based on the process of hydrolysis. It is found in most gummy candy, as well as other products such as marshmallows, gelatin desserts, and some ice creams, dips, and yogurts. Gelatin for recipe use comes in the form of sheets, granules, or powder. Instant types can be added to the food as they are; others need to be soaked in water beforehand.