Résumé : Since the approval of the Sustainable Development Goals (SDGs) by the United Nations General Assembly in 2015, there has been an extensive debate, both politically and academically, on how to assist the Least-Developed Countries (LDCs) in achieving those targets before 2030. As the former United Nations Secretary General Ban Ki-Moon linked the failure of the predecessors of the SGDs, the Millennium Development Goals (MDGs), to the “inadequate resources” (United Nations, 2010), the never-ending debate over development aid revamped: is aid necessary? In which amount? Is it always good and needed? Which is the most efficient modality of delivering it?The aim of this dissertation is to study the relationship between official development assistance (ODA) and institutions under a perspective which is mainly ignored by the literature: how does aid affect institutional stability? The study is carried out in the framework of Ian Bremmer’s J curve, a theory that provides useful insights on the relationship between aid and stability. The main thesis here supported is that aid can be both a enhancer of stability or a catalyzer of instability: working as a form of external rent, development assistance increases inter-group competition, which in (especially ethnically) divided society may fuel conflict and instability. On the other hand, if appropriate mechanisms are in place, then aid gives to the ruling elite a valuable contribution in strengthening national capacities, thus having a positive impact on stability.This study focuses on Sub Saharan Africa, and in particular it analyses the case of Rwanda. Since its independence, the small Central African country has lived a complicated history, marked by ethnic tensions and conflicts, until its nadir in 1994 with the Tutsi genocide. This thesis studies how aid contributed to the explosion of violence in the country and what changed since those dramatic days; now Rwanda is a strong performer in terms of development in the African country, and an important role has been played by aid. How did ethnic relations change? Which mechanisms were put in place? How has development assistance changed its effects on the Rwandese society? All of these questions are analyzed to understand how aid can enhance or reduce institutional stability.