Official Development Assistance (ODA) was introduced in the 1960s as a temporary instrument to respond to a particular moment in history, amid decolonisation, the Cold War, industrialisation and poverty reduction efforts in the ‘Global South’. But in a world where the lines between ‘developed’ and ‘developing’ countries is increasingly blurred; where strained development budgets are not growing in line with growing needs; where geopolitical polarisation between North and South is building historic levels of distrust; and amid a rejection of a donor-recipient model of aid-induced development as charity, the traditional rationale for aid has reached its limits. This is the backdrop for an era ODI is calling a ‘post-aid’ world. A post-aid world does not mean acute global needs do not exist, nor that donors are completely shirking their efforts to address them. Rather, it is a reference to a crisis of legitimacy and relevance for the entire endeavour of Northern donorship.