This paper has two aims. The first is to describe several sources of the moral responsibility to remedy or alleviate global poverty—reasons why an agent might have such a responsibility. The second is to consider what sorts of agents bear the responsibilities associated with each source—in particular, whether they are collective agents like states, societies, or corporations, on the one hand, or individual human beings on the other. We often talk about our responsibilities to the poorest people in the world, or what we owe them. So the question is who this we is. I shall argue that the answer depends on the source of the responsibility. Some responsibilities—one species of causal responsibilities—belong in the first instance to collectives, although they will also trickle down to at least some individuals within the collective. Other responsibilities—humanitarian responsibilities, and a different species of causal responsibilities—belong in the first instance to individuals, but can, I shall argue, “trickle up” to collectives of which individuals are members.