Worldwide there is a growing perception among intellectuals, politicians and citizens, that current global problems and conflicts cannot be solved by national governments, even not by the most powerful ones. It is also more and more observable that the current multilateral institutions (UN, World Bank, IMF, WTO, etc.), created in the aftermath of the Second World War to administrate political stability and economic prosperity, can no longer deliver in today's fully informed, much more democratic and highly interconnected world. Moreover, the pervasive promotion of national democracies across the world - as currently 'pursued' by the West - to solve problems of a collective nature (global public goods and global externalities) is neither a necessary nor a sufficient condition. Indeed, developments in the last decade have proven that at global level, and in crucial areas such as peace and common security, global environment, etc., a UN led by self-appointed 'nationally democratic' arbitrators, cannot deliver.In fact, in such circumstances and following the principle of self-interest, even nationally democratic countries have often behaved as free-riders in global economic issues, while the most powerful, in absence of balanced political costs, have tended to abuse the others. In addition, dominant neo-conservative policies in the last two decades have mostly resulted in worse national and international income distribution, increased the number of conflicts and tensions across the world, and been incapable of dealing with common-global problems such as climate change. Against the above global political background, the authors, after carefully analyzing the foundations of democracy at national and global levels, the conditions for sustainability of democracy, and its interconnections with capitalism - be this national or global - propose a complete redesign of the UN system and its economic agencies on a democratic basis. According to the authors, this will finally result in a global democracy for exclusively dealing with global public goods and externalities.A priority target of this reorganization will be a more balanced and acceptable global distribution of income, as a necessary condition for the survival of global capitalism. The authors, after carefully analyzing the foundations of democracy at national and global levels, the conditions for sustainability of democracy, and its interconnections with capitalism - be this national or global - propose a complete redesign of the UN system and its economic agencies.