The twenty-four month period leading up to the Paris climate negotiations last December, also known as COP 21, represented, by almost any measure, a high water mark of the religious-environmental movement. Never before have religious groups around the world within such a concentrated period of time shown such a level of public support for environmental action. This essay represents an effort to chronicle some of this activity and demonstrate the substantial and multi-faceted growth of this movement, and then introduces the other articles and essays in this issue of the Journal of Inter-religious Studies, of which I (on behalf of GreenFaith) serve as guest editor. In doing so, it highlights some of the questions, developmental challenges, and new dimensions of a movement that has steadily emerged from the margins of religious life, to represent an increasingly strong center of gravity for interfaith organizing on a global scale.