This chapter reviews the main international environmental treaties promoted by the United Nations (UN), emphasizing the organization’s pivotal role in global environmental governance and its success in placing climate change at the forefront of the international political agenda. Despite these achievements, the UN faces numerous structural and political barriers that limit its capacity to implement effective environmental policies. Some of these constraints include institutional fragmentation, competition among agencies, the political interests of Member States, or financial limitations, among others. Thus, to overcome these challenges, greater coordination and reform within the UN system will be necessary, along with genuine integration between politics, science, and society. Only in this way we can achieve intergenerational and climate justice and establish a global environmental governance that is equitable and sustainable over time.