This review critically assesses a large and growing literature on multiactor environmental governance. The first section provides an historical and conceptual background to the observed increase in such arrangements. The second section describes the diversity of governance arrangements and the related actor constellations to address environmental issues, and the third section offers some explanations for the origins, form, and effectiveness of multiactor governance arrangements. The conclusion reflects on some of the key challenges in advancing and deepening research in this area and suggests some fruitful avenues for future work.