Northwestern Sahel represents one of the most unstable areas in sub-Saharan Africa. Seven years after the outbreak of the conflict in Mali, violent extremism has spread across the region, together with community conflicts over the access to natural resources and inter-ethnic violence. Trans-border activities of non-state armed actors – insurgents, jihadist groups and ethnic-based militias – as well as illicit trafficking networks feed the regional insecurity. These dynamics have boosted military and political intervention of Western actors and the development of multilateral initiatives across Mauritania, Mali, Niger, Burkina Faso and Chad. What are the main drivers of the instability affecting the Sahelian states? To what extent is the current security situation in the Sahel deteriorating? And what are the challenges ahead for states and international actors?