In slogan form, holism is the obscure thesis that the whole is more than the sum of its parts. Physics has been taken to exhibit holism of various kinds, associated with different ways of trying to make this thesis clear. On a more metaphysical approach, holism is the view that the existence or features of some physical whole are not determined by the existence and features of its constituent parts. This chapter discusses methodological holism in physics and considers whether the physical theories imply such metaphysical holism. While some form of ontological holism has occasionally been considered, the variety of metaphysical holism most clearly at issue in quantum mechanics is property holism. One may try to avoid the conclusion that experimental violations of Bell inequalities manifest a failure of Local Action by invoking ontological holism for events.