生物降解垃圾（英语：Biodegradable waste）包含所有能借由堆肥、好氧消化、厌氧消化等类似过程被微生物或生命体分解成二氧化碳、水、甲烷和简单有机分子的废弃有机物。生活中常见者为食品废弃物，又称厨余、馊水或剩食，是食物于烹煮前食材处理所剩或食用后所剩之统称。由于「废弃物」的定义不一，许多国际组织、政府机关、专业机构对食品废弃物都有各自的定义。

厨余又可分为生厨余和熟厨余，前者为烹煮前食材物料处理所剩之物。（菜叶、果皮等均属），后者为经烹煮食用所剩之物。（剩叶、饭、骨、汤水等均属）

Biodegradable waste includes any organic matter in waste which can be broken down into carbon dioxide, water, methane or simple organic molecules by micro-organisms and other living things using composting, aerobic digestion, anaerobic digestion or similar processes. In waste management, it also includes some inorganic materials which can be decomposed by bacteria. Such materials include gypsum and its products such as plasterboard and other simple organic sulfates which can be decomposed to yield hydrogen sulfide in anaerobic land-fill conditions.