We review psychological research on global human identification and citizenship, Thomas Paine's belief that "The world is my country, and all mankind are my brethren." In turn, we review the theoretical foundations that guided our work, research with measures that preceded our own, and our own work with our correlated scales. We review its foundations, its effects upon attitudes and behaviors, and how it might be enlarged. Global human identification and citizenship is related negatively to ethnocentrism, authoritarianism, the social dominance orientation, and self-centeredness, but positively to dispositional empathy, openness to experience, and the values of universalism, care, and justice. It is expressed in attitudes and behaviors that support human rights and work to reduce global suffering and inequalities. It is associated with greater global knowledge and with efforts to acquire that knowledge. Childrearing that emphasizes cross-cultural exposure and awareness of others' suffering may promote global human identification and citizenship, as does education that encourages global mindedness. Environments that support global human identification also induce it, as does envisioning it as a moral ideal.