Entosis is a mechanism of cell-in-cell formation that resembles phagocytosis but is regulated by distinct processes related to cell-cell adhesion and actomyosin tension. Entosis results in the engulfment of cells with high levels of tension, which become internalized into cells with lower tension, following the formation of adherens junctions between the pair. The resulting “cell-in-cell” structures typically resolve in a manner that leads to the death of the internalized cells, although other fates, including internalized cell release, are also possible. Entosis is induced in response to a variety of stressors, sometimes in parallel to other forms of cell death, and has been observed to occur in cancer as well as normal tissues. Here we discuss the mechanism of entosis and consider its unique properties compared to other forms of cell death and engulfment.