The consolidation of political authority over Southern Sudan has never been achieved, nor has the region ever experienced a comprehensive, uniform system of governance. No one political group, external or internal, has ever been able to present itself as the legitimate representative of the populace of Southern Sudan. These, however, were the objectives which the Sudan People's Liberation Movement (SPLM) sought to achieve from 2005 to 2010. The main contention of this thesis is that the success or failures of the SPLM at post-conflict state-building can be measured through the conceptual framework of legitimacy. As a rebel movement, the SPLM fought a war of liberation against the government of Sudan from 1983 to 2004. Yet, the SPLM was not fighting for the secession of the South, as its predecessor had, but for the liberation of the country and for the creation of a 'New Sudan' where all the politically marginalised groups of Sudan would be political equals. The movement based its rationale on a 'revolutionary ideology', but this form of ideological legitimation was insufficient to gain Southern-wide support for its cause. The movement failed to establish rebel governance structures, was accused of abuses against the local population, and generally looked to external actors for support. Yet, through a peace agreement largely propelled forward by the United States, the SPLM 'won' the war and was tasked with constructing a semi-autonomous state in Southern Sudan. The successes or failures of the SPLM in developing the Government of Southern Sudan were largely dependent on its ability to create effective institutions and consolidate legitimacy. In order to accomplish this, the SPLM would have to shed its militaristic ethos and revolutionary ideology and thereby enable it to govern not as a rebel movement but as a political party. This, however, did not take place. The new Southern Government, which was supposed to be developed along the lines of a decentralised system of governance, remained centralised. The state and county governance institutions did not undergo the necessary capacity-building and were, subsequently, not able to provide for the security, development or welfare of the Southern populace. Thus, the government failed to consolidate eudaemonic legitimacy. In light of this shortcoming, government officials and the SPLM leadership promoted civic and revolutionary ideology as means to consolidate support. While ideological legitimation was successful to a certain extent, the majority of the Southern populace was illiterate and living in poverty; concepts such as democracy, civic responsibility or SPLM successes during in the peace process were not as appealing as the provision of basic services and development. Thus, the inability of the government to provide for the needs of the citizens jeopardised the attempts at ideological legitimation. As long as the government remained centralised and paralysed in providing for the welfare of the Southerners, it was unable to be considered as the true representative of the populace.