This paper examines some key statebuilding challenges confronting South Sudan in the aftermath of the January 2011 referendum that separated this region from the Republic of Sudan. Following the referendum, the two states—the Republic of Sudan and South Sudan—face the immediate challenge of negotiating the terms of their relationship over a number of critical issues, including: the future of the contested border town of Abyei, the problem of how to divide oil revenues, the definition and demarcation of the border between the two entities, and the establishment of a citizenship regime. At the same time, even if a settlement between the two over these issues was reached, South Sudan’s internal political, security and developmental challenges remain enormous. For the foreseeable future, South Sudan will remain a fragile state in need of international assistance and support. In conclusion, this paper briefly assesses the implications of the birth of South Sudan for other simmering conflicts and for the doctrine of self-determination.