The health of the planet and its life forms are under threat from anthropogenic climate change, pollution and biodiversity loss, and the extreme weather events, heatwaves and wildfires that accompany them. The burgeoning field of planetary health studies the interplay between humanity and the Earth’s biosphere and ecosystems on which human health depends. Scholarship on law from a planetary health vantage point remains scarce. This article fills this gap by delineating the conceptual building blocks of a planetary health law, which, in its latent form, is dispersed across various hard and soft sources of international environmental law and global health law that converge on the right to a healthy environment, and, to a lesser extent, rights of nature emerging in various domestic jurisdictions. It elucidates how the fragmented regimes of international environmental and global health law could be developed in more coherent ways, driven by an overarching concern for the integrity of the planetary foundations of life.