This chapter presents soil as a major element for forests, emphasizing its importance as a fundamental component of the environment and terrestrial life. It delves into the processes of soil formation, known as pedogenesis, and their continuous evolution under the influence of geological, climatic, and biological factors. Composed primarily of minerals and organic matter, soil plays a crucial role in water regulation, fertility, and pollutant filtration. It is also a key player in food production and biodiversity preservation. The chapter highlights the various ecological functions of soil, emphasizing its role as a carbon sink, greenhouse gas regulator, and genetic reservoir. It also explores the challenges related to soil degradation and human activities, such as urbanization and agricultural intensification, which threaten this vital ecosystem.