The Great Green Wall or Great Green Wall of the Sahara and the Sahel is a project adopted by the African Union in 2007, initially conceived as a way to combat desertification in the Sahel region and hold back expansion of the Sahara desert, by planting a wall of trees stretching across the entire Sahel from Djibouti, Djibouti to Dakar, Senegal. The original dimensions of the "wall" were to be 15 km wide and 7,775 km long, but the program expanded to encompass nations in both northern and western Africa. The concept evolved into promoting water harvesting techniques, greenery protection and improving indigenous land use techniques, aimed at creating a mosaic of green and productive landscapes across North Africa. Later it adopted the view that desert boundaries change based on rainfall variations.

Richard St. Barbe Baker, Hon. LL.D. F.I.A.L., For.Dip.Cantab., ACF was an English biologist and botanist, environmental activist and author, who contributed greatly to worldwide reforestation efforts. As a leader, he founded an organisation, Men of the Trees, still active today as the International Tree Foundation, whose many chapters carry out reforestation internationally.