This book examines the impact of applying the “terrorist” label to a group’s choice to resort to violence within an ethnonationalist conflict. Using the Partiya Karkerên Kurdistanê (PKK) in Türkiye as a primary case study, the book interrogates the socio-political ramifications of the Turkish government’s decision to label the PKK as a terrorist organisation. Drawing on longitudinal interviews, newly opened Turkish and Kurdish archives, media frame databases, and casualty logs, it maps five decisive moments: the 1984 guerrilla launch; Abdullah Öcalan’s 1999 arrest; the 2012–2015 peace talks; Kobani’s stand against ISIS in 2015 in a town in Syria; and the 2025 stand down. Furthermore, the study’s empirical analysis and discussions reveal that the invocation of the label “terrorist” against the PKK places the group’s actors and sympathisers in a situation that makes it harder for them to engage in peaceful means of resolving the conflict. Using four waves of interviews with Kurds in Türkiye and Syria spanning over a decade, the book offers dynamic insights into how attitudes towards the PKK and the “terrorist” label have shifted over time. This book will be of interest to students and scholars of terrorism and political violence, ethnic conflict, critical security studies, and international relations.