Under what conditions do you have a reason to perform some action? Do you only have reason to do what you want to do? Reasons-motives internalism is the appealingly simple view that unless an agent is, or could be, motivated to act in a certain way, he has no normative reason to act in that way. Thus, according to reasons-motives internalism, facts about an individual’s motivational psychology constrain what is rational for that agent to do. This article canvasses several ways of formulating the view and considers some advantages and disadvantages of each.