Autophagy (or autophagocytosis) (from the Greek auto-, "self" and phagein, "to eat"), is the natural, destructive mechanism that disassembles, through a regulated process, unnecessary or dysfunctional cellular components.

Autophagy allows the orderly degradation and recycling of cellular components. During this process, targeted cytoplasmic constituents are isolated from the rest of the cell within a double-membraned vesicle known as an autophagosome. The autophagosome then fuses with a lysosome and the contents are degraded and recycled. Three different forms of autophagy are commonly described: macroautophagy, microautophagy and chaperone-mediated autophagy. In the context of disease, autophagy has been seen as an adaptive response to stress, which promotes survival, whereas in other cases it appears to promote cell death and morbidity. In the extreme case of starvation, the breakdown of cellular components promotes cellular survival by maintaining cellular energy levels.