This thesis examines the political trajectory of the Popular Front for the Liberation of Palestine (PFLP) during the period from the 1982 eviction of the Palestinian factions from their headquarters in Beirut, to the 2006-07 division between Hamas and Fatah in the Occupied Palestinian Territories (OPT). During this period, the PFLP experienced a process of decline that resulted in its marginalisation within the Palestine Liberation Organisation (PLO) and the wider Palestinian national movement. This study addresses the issue of the PFLP’s decline by focusing on its own political agency to determine the role of policy and decision making, ideology and political narrative in the marginalisation process. This work therefore, on the one hand, aims at putting the PFLP’s decline into historical perspective, identifying it as a process rather than simply the effect of outstanding events as it is often argued. On the other, its goal is to ascribe to ‘subjective factors’, namely aspects directly linked to the PFLP’s agency, the adequate weight in determining its decline. This appears particularly significant as the weakening of the Palestinian left has been frequently explained as a by-product of global and local external or ‘objective’ developments such as the downfall of the Soviet Union or the emergence of political Islam. By providing a comprehensive and processual analysis of the PFLP’s decline, this study not only aims at complementing the literature on the Palestinian national movement, which still lacks a focused approach on the main Palestinian leftist force. It also aims at shedding light on a major cause, and its historical origins, of the current Palestinian political impasse, namely the absence of an alternative between Hamas and the PNA’s governing entities, both crippled by a legitimacy crisis and unable to progress Palestinian interests. By virtue of its close survey of the PFLP’s conduct, a further goal of this thesis is to address the historical role of the PLO and its de-facto heir, the PNA. What is evidenced is the double, and contradictory, role of the essential but also constraining framework that the PLO and later the PNA represented for the PFLP’s policies. The focus on the PFLP’s political agency allows the identification of a pattern in its policy which affected negatively its standing within the Palestinian national movement. Throughout the period addressed, policy fluctuation marked the PFLP’s action, undermining the effectiveness of its political line and jeopardising its political weight. The present study highlights how such a policy fluctuation pattern originated from major dilemmas and contradictions that the PFLP had to consider while producing its policies. The main dilemma, informing all other sources of tensions affecting the PFLP, has been defined as an ‘opposition-integration’ dilemma. In other words, the PFLP, while opposing the PLO leadership’s policies, first and foremost its quest for a diplomatic settlement with Israel under US patronage, needed to maintain its integration within the PLO regime, which represented an essential economic and political framework. This produced inconsistent, ‘fluctuant’ policies that prevented the PFLP from maintaining its political weight and stopping its marginalisation process. This opposition-integration dilemma was combined with other sources of tensions marking the PFLP such as: relations with other PLO opposition factions, relations with Arab partners, its contacts with Palestinian Islamists, the confrontation with the PNA after the 1993 Oslo accords or the internal divide between the exiled leadership and the cadres located in the OPT. The PFLP’s official publications, mainly retrieved from its mouthpiece, Al-Hadaf magazine, embodied the main source upon which this study relies. Beside this corpus of documents, other primary sources, such as documents issued by relevant actors, have been scrutinised, while all information has been read against the background of the wider academic literature currently available on the Palestinian national movement. This research also drew information from interviews with former and current PFLP members as well as with experts of the Palestinian national movement.