This article retraces the history of fertility theories as illustrated by 23 founding texts grouped together in a single volume (Leridon, 2014, Les théories de la fécondité, INED). Until recent times, no reliable statistics were available for the analysis of fertility behaviours, which were treated rather as a question of philosophy, morals, political science or religion. It was not until the birth of the social sciences in the nineteenth century that the first real theories of fertility started to emerge. At that time, the demographic transition in Europe and the accompanying social and economic transformations gave rise to new demographic behaviours for which a theoretical framework was needed. Many new disciplines were brought into play, including anthropology, sociology, economics, political science and psychology. Paradoxically, demographers were slow to develop theoretical approaches, doubtless because the discipline first made its name as a quantitative science. Indeed, no overarching, generally acknowledged theory of fertility has yet been developed. These different approaches are illustrated through a series of pioneering texts. They present theories drawn from a wide range of disciplines and include analyses from the perspectives of birth control and gender.