One of the most widely used concepts in the sociology of women and men's work is that of the breadwinner. Given its centrality to and in so many core academic debates, it is surprising that so little attention has been paid to theorizing and operationalizing breadwinning. Breadwinning seems to lie uncontested, with an unproblematic taken-for-granted, common sense meaning in current sociology. The article reviews how breadwinning has been approached in sociology and how it has been operationalized in empirical studies.