This chapter explores the theoretical critiques that environmental politics attracted since the 1990s onward. Among them, building upon political ecology critique, post-environmentalist theory gained a prominent role and claimed that green diplomacy, business, and large NGOs determined a de-politicization of environmental issues in the pursuit of establishing a widespread consensus on the mainstream strategies for global environmental governance. The origins and development of post-environmentalism are described in the chapter, with particular attention devoted to the differences between the realist perspective of US scholars (most notably Michel Shellenberger and Ted Nordhaus, authors of the pamphlet “The Death of Environmentalism”) and the European scholars, advancing a constructivist interpretation of the end of environmentalism under the name of post-ecologism.