The normative notion of fittingness figures saliently in the work of a number of ethical theorists writing in the late nineteenth and mid-twentieth centuries and has in recent years regained prominence, occupying an important place in the theoretical tool kits of a range of contemporary writers. Yet the notion remains strikingly undertheorized. This article offers a (partial) remedy. I proceed by canvassing a number of attempts to analyze the fittingness relation in other terms, arguing that none is fully adequate. In explaining why various analyses of fittingness fail, I draw into relief certain of the relation’s constitutive features and spotlight some of its interesting and important connections to various other properties. Along the way, I highlight the relation’s relevance to a number of ongoing debates in normative and metanormative philosophy. I conclude by indicating some directions for further research.