Multilateral diplomacy is the management of international relations by negotiations among three or more states through diplomatic or governmental representatives, but it can also be engaged in by representatives of non-state actors. Multilateral negotiation is characterized by multi-parties, multi-issues, multi-roles, and multi-values. The level of complexity is far greater than in bilateral diplomacy as is the level of skill needed to manage that complexity. It can be based on multilateralism, or have multilateralism as a goal, but it can also be pursued by those who do not. Multilateralism can be defined as global governance of the many, and a major principle is the opposition to bilateral discriminatory arrangements. Classic diplomatic studies focused on bilateral diplomacy. However, the growth of international organizations in the 20th century increased interest in multilateral diplomacy, which has developed since its origins in 1648. Increasing attention has been paid to the role of non-state actors and new forms of diplomacy affected by globalization and the digitization of information. In the 21st century, multilateral diplomacy faces unique challenges and calls for reform of international organizations and global governance.