This book develops a new theory of territorialism and international legal status of territories. It (i) defines the concept of territory, explaining how territories are created; (ii) redefines the concept of statehood, illustrating that statehood (rather than the statehood criteria) is territorial legal status established in the formal sources of international law; and (iii) grounds non-state territorial entities in the sources of international law to explain their international legal status. This fresh new theoretical perspective has both scholarly and practical importance, providing a tool helping decision-makers and judges in the practical application of international law both internationally and domestically.