Why do we need the green state to combat environmental problems? In this chapter, I highlight the key challenges the state faces in governance for sustainable development (GSD) with regard to policy, polity, and political dimensions, and elucidate and discuss the functions and responsibilities the green state brings to efforts to address these challenges. The green state possesses a unique capacity and legitimacy to foster and lead the transition towards a more sustainable society. Rather than being neglected or lost within the scholarly field of GSD, the state should be brought forward as an important actor in governance for sustainable development.