On a general level, the significance of personality in international law is straightforward. In analogy to the use of personality in municipal law, it is to distinguish those social actors belonging to the international legal system from those being excluded from it. International persons can claim direct protection by international law or are subjected to obligations determined by it whereas entities not having that status generally cannot do so for they do not directly exist for the international legal system. On a more specific level, however, it is more difficult to detect the significance of international personality. The topic, as has been noted, often looms in the background of legal argument and is rarely directly addressed in legal practice. But this does not mean that it is not relevant for legal outcomes. One's conception of international personality, it is submitted, significantly influences international legal issues. In particular, it often determines the starting point of legal analysis and eventually its outcome. In the following, this is illustrated by means of four legal situations in which the choice of a particular conception of international personality has important legal effects: (a) the direct application of treaties to individuals, (b) responsibility of international organizations, (c) the rights and duties of non-state actors under customary international law, and (d) the applicable law to so-called state contracts.