Development can be defined in many ways, but here is taken to be an explicit process involving resources, policies, services, and programs deployed by the state and other actors with the aim of achieving economic growth and social wellbeing for a given population. International development refers to initiatives advancing this agenda in low-and middle-income countries (LMICs) specifically. It is widely acknowledged that there is good reason to prioritize children (defined as all individuals under the age of eighteen) in such processes, and the young have now become central to the international development agenda and to national development policies throughout the world. This trend reflects the high proportion of young people relative to total population across many LMICs, recognition of the urgent need to ameliorate the dire conditions faced by countless boys and girls in these settings, and a dramatic expansion of child-focused policies, services, and interventions in recent decades.Two distinct arguments are advanced for channeling development efforts toward the young. The first is shaped by notions of universal justice and human rights and works from the premise that children are inherently vulnerable and dependent and are hence especially deserving of support and protection. They are marked out from other generations as carriers of a distinct set of rights to be safeguarded by designated duty bearers, particularly states and parents. This case finds expression in international child-rights instruments developed over the course of the twentieth century, culminating in the 1989 UN Convention on the Rights of the Child (CRC). Here, prioritizing the young in development processes is about applying the concept of rights to achieve agreed international standards for all children everywhere with regard to their survival, development, protection, and participation. The second line of reasoning highlights the threat to life and developmental potential resulting from poverty and other preventable risks to children in LMICs. The first thousand days of life are underlined as the most crucial for child survival and development; recovery from nutritional deprivation or other shocks experienced during this period, it is argued, is highly unlikely, if not impossible. Economists have pursued this line of thinking further in the application of the human-capital framework by underscoring the consequences of early-life deprivations for adult productivity, thereby also drawing attention to the implications for national economic prospects; thus, this particular model is as much about national interests as about the wellbeing of the current generation of young.