In cell biology, autophagy, or autophagocytosis, is a catabolic process involving the degradation of a cell’s own components through the lysosomal machinery. It is a tightly regulated process that plays a normal part in cell growth, development, and homeostasis, helping to maintain a balance between the synthesis, degradation, and subsequent recycling of cellular products. It is a major mechanism by which a starving cell reallocates nutrients from unnecessary processes to more-essential processes.

A variety of autophagic processes exist, all having in common the degradation of intracellular components via the lysosome. The most well-known mechanism of autophagy involves the formation of a membrane around a targeted region of the cell, separating the contents from the rest of the cytoplasm. The resultant vesicle then fuses with a lysosome and subsequently degrades the contents.

It was first described in the 1960s, but many questions about the actual processes and mechanisms involved still remain to be elucidated. Its role in disease is not well categorized; it may help to prevent or halt the progression of some diseases such as some types of neurodegeneration and cancer, and play a protective role against infection by intracellular pathogens; however, in some situations, it may actually contribute to the development of a disease.