Autophagy is a highly conserved pathway for physiological metabolism. Bilayer vesicles transport their contents to lysosomes for degradation. Autophagy is therefore a means of removing intracellular viruses and other pathogens in mammalian cells. However, the role of autophagy in virus infection is complex. Several viruses have developed a way to escape autophagy-dependent degradation and replicate themselves through autophagy. This article summarizes the fundamental mechanism and function of autophagy and its role in infection with viruses such as HIV, HTLV-1, and other retroviruses.