This paper, a distillation of findings from the NYU Global Administrative Law Research Project, considers the emergence and the need for further development of administrative law mechanisms to promote greater accountability in decisionmaking and rulemaking in the rapidly proliferating variety of global regulatory structures. These include formal international organizations (such as the WTO, the Security Council, World Bank, the Climate Change regime, etc), informal intergovernmental networks of domestic regulatory officials (such as the Basel Committee of national bank regulators), domestic authorities implementing global regulatory law, hybrid public-private and purely private transnational regulatory regimes. The subjects of such global regulatory systems include individuals, firms and other economic actors, states, and occasionally NGOs. These regimes and subjects, we argue, are part of a single global administrative space distinct from the domains of international law and domestic administrative law. We define global administrative law as the principles, procedures, and review mechanisms that are emerging to govern decisionmaking and regulatory rulemaking by these bodies. We identify a number of structural mechanisms that have arisen to develop and apply global administrative law, including domestic courts and legislatures reviewing domestic implementation of global standards and national officials' participation in global administrative decisions, and new mechanisms developed at the global level for governance of international and transnational regulatory bodies. We examine the sources and content of the various doctrinal principles and requirements that have been developed and enforced by these mechanisms (such as transparency, participation, reasoned decisionmaking, review, and substantive standards such as proportionality), and their sources. We next consider the normative foundations of global administrative law, including intra-regime control, liberal notions of protection of the rights of individuals and of economic actors, protection of the rights of states, and securing democracy with respect to global regulation. We examine these normative foundations in relation to three conceptions of international ordering - pluralist, solidarist, and cosmopolitan - and in relation to North-South differences. We then consider different strategies for constructing global administrative law, including bottom-up approaches that seek to extend domestic administrative law to global regulatory decisions and top-down approaches that develop new administrative law mechanisms at the global level. We also examine the positive political theory of global administrative law. We conclude that the field of global administrative law is an important emerging phenomenon, distinct from international law and from domestic administrative law, that deserves systematic study and development.