The scope of this graduation project is the study of two domains, (1) territorialism and territoriality, (2) contested and conflicted environments. These domains are discussed in relation to spatial planning. The project examines the ongoing conflict in Cyprus as the main case study. Particularly, it studies the manifestations of territorialism through analyzing how the border between the two contested territories transformed over time. The outcomes of the territorial division of the island caused by the Turkish invasion in 1974 are examined firstly. Secondly the outcomes of the re-bordering of the green line in 2003 and henceforth are investigated. Results from this analysis, identify a broad variety of existing territories with a different status. Additionally, they demonstrate a lack of effective bi-communal cooperation and planning that is adequate to meet particular environmental challenges. Results also show the potential for more territorial cooperation through different domains, based on the existing socio-spatial conditions. Outcomes of the analysis are used to define new territorial cooperation with responsibilities that are shared across communities, and a more important, mediating role for supra-national authority and an increased focus on environmental challenges. These are used to propose a spatial plan¬ning framework for conflict mediation, that will activate sustainable development in Cyprus, addressing the direct and indirect outcomes of the deficiencies of territorialism.