Welfarism is a theory of value (or the good) simpliciter. Theories of value are fundamentally concerned with explaining what makes some possible worlds better than others. Welfarism is the view according to which the relative value of possible worlds is fully determined by how individuals are faring—or, in other words, by the facts about well-being that obtain—in these worlds. This entry begins by distinguishing between various forms of welfarism (pure vs. impure welfarism, and then narrow vs. wide welfarism). It then outlines some of the key attractions of welfarism. Finally, it surveys some of the most serious objections to welfarism (including malicious pleasure, the well-being of the wicked, great works of art, the non-identity problem, human extinction, transitivity of betterness, and distribution).