Scientists around the world are actively working toward de-extinction, the concept of bringing extinct species back to life. Before herds of woolly mammoths roam and flocks of passenger pigeons soar once again, the international community needs to consider what should be done about de-extinct species from a legal and policy perspective. In the context of international environmental law, the precautionary principle counsels that the absence of scientific certainty should not be used as an excuse for failing to prevent environmental harm. No global legal framework exists to protect and regulate de-extinct species, and this Article seeks to fill that gap by anticipating how the global legal framework for de-extinction could be structured. The Article recommends that the notions underlying the precautionary principle should be applied to de-extinction and that the role of international treaties and other international agreements should be considered to determine how they will or should apply to de-extinct species. The Article explains the concepts of extinction and de-extinction, reviews relevant international treaties and agreements, and analyzes how those treaties and agreements might affect de-extinct species as objects of trade, as migratory species, as biodiversity, as genetically modified organisms, and as intellectual property. The Article provides suggestions about how the treaties and the international legal framework could be modified to address de-extinct species more directly. Regardless of ongoing moral and ethical debates about de-extinction, the Article concludes that the international community must begin to contemplate how de-extinct species will be regulated and protected under existing and prospective international laws and policies.