The collapse of state authority in Libya after the 2011 uprising has produced a chain of security consequences that continue to shape the wider Sahel. This paper examines how the Libyan conflict created conditions that encouraged the spread of terrorist activity across the region, with particular attention to arms proliferation, the movement of foreign fighters and the growth of ungoverned spaces that allow violent groups to operate with relative freedom. The study draws on a qualitative case study design supported by interview material from the wider research, which provides grounded insight into how Libya’s internal fragmentation became linked to regional insecurity rather than remaining a self‑contained crisis. Rather than treating Libya as an isolated arena of state collapse, the paper conceptualises it as a catalytic node within a wider ecosystem of fragile states, porous borders and historically marginalised communities.

The analysis is informed by state fragility theory and relative deprivation perspectives. These frameworks help explain how the breakdown of governance structures in Libya interacted with long‑standing political and economic pressures in neighbouring Sahelian states. The argument shows that Libya’s collapse intensified existing vulnerabilities in Mali, Niger and Chad, encouraged the circulation of weapons and fighters, and weakened already fragile border management systems. These developments strengthened the operational reach of armed groups and complicated national and regional attempts to respond to rising insecurity.

The paper contributes to regional security research through three main insights. It clarifies the pathways through which local state collapse can generate transnational terrorist dynamics. It demonstrates the value of analysing conflict spillover through a multi‑level lens that links domestic governance failures to regional patterns of violence. It also highlights the limitations of current security responses that treat Sahelian states as discrete units rather than parts of an interconnected security landscape. The study offers a grounded and theoretically informed account of how Libya’s post‑2011 crisis has reshaped security conditions across West and North Africa and points to the need for more coordinated and context‑sensitive regional strategies.