The Sahel—the belt of land that stretches across Africa on the southern edge of the Sahara—has always been a tough place to farm. Rainfall is low and droughts are frequent. The crust of hard soil is, at times, almost impermeable, and harsh winds threaten to sweep away everything in their path. Over the past three decades, however, hundreds of thousands of farmers in Burkina Faso and Niger have transformed large swaths of the region’s arid landscape into productive agricultural land, improving food security for about 3 million people. Once-denuded landscapes are now home to abundant trees, crops, and livestock. Although rainfall has improved slightly from the mid-1990s relative to earlier decades, indications are that farmer management is a stronger determinant of land and agroforestry regeneration. Sahelian farmers achieved their success by ingeniously modifying traditional agroforestry, water, and soil-management practices. To improve water availability and soil fertility in Burkina Faso’s Central Plateau, farmers have sown crops in planting pits and built stone contour bunds, which are stones piled up in long narrow rows that follow the contours of the land in order to capture rainwater runoff and soil. These practices have helped rehabilitate between 200,000 and 300,000 hectares of land and produce an additional 80,000 tons of food per year. In southern Niger, farmers have developed innovative ways of regenerating and multiplying valuable trees whose roots already lay underneath their land, thus improving about 5 million hectares of land and producing more than 500,000 additional tons of food per year. While the specific calculations of farm-level benefits are subject to various methodological and data limitations, the order of magnitude of these benefits is high, as evidenced by the wide-scale adoption of the improved practices by large numbers of farmers. Today, the agricultural landscapes of southern Niger have considerably more tree cover than they did 30 years ago. These findings suggest a human and environmental success story at a scale not seen anywhere else in Africa. The re-greening of the Sahel began when local farmers’ practices were rediscovered and enhanced in simple, low-cost ways by innovative farmers and nongovernmental organizations. An evolving coalition of local, national, and international actors then enabled large-scale diffusion and continued use of these improved practices where they benefited farmers.