Trust in international actors, from nations in general to specific international governmental organizations and nationalities, can shape how citizens form judgments about international relations. This chapter examines the nature, levels, foundations, and consequences of such trust among mass publics, particularly the US public. Survey data from the past three decades reveal low levels of generalized trust in other nations. This form of trust reflects changes in the international environment along with individual-level demographics, social trust, political trust, partisanship, ideology, and media use. Trust in other nations is linked to an array of foreign policy opinions as well as evaluations of individual nations and trust in international organizations. Citizens’ beliefs about how much they can trust international actors provide them with information shortcuts for forming views about world affairs but may create obstacles to international cooperation.