The dehesa (or montado) is a traditional agrosilvopastoral agroforestry system in the southwestern Iberian Peninsula, characterized by scattered Quercus spp. trees, native livestock breeds, and a diverse herbaceous layer. Recognized for its high natural, cultural, and economic value, the dehesa provides crucial ecosystem services, supports biodiversity, and represents a unique cultural landscape. However, this system faces significant contemporary challenges that threaten its long-term sustainability. These include land degradation (e.g., soil erosion, tree mortality), a critical lack of tree regeneration, and pressures from socio-economic changes such as the abandonment of traditional practices, agricultural intensification, and the impacts of climate change. This chapter synthesizes the dehesa’s ecological and socio-economic characteristics, explores its inherent complexities, and the principal drivers of its degradation. It emphasizes the importance of understanding the dehesa as a complex socio-ecological system where management practices are integral to its structure and function. Critical factors are highlighted such as tree regeneration failure, soil health, and the impact of agricultural policies, while some strategies for sustainable management are considered, including facilitating tree regeneration, promoting traditional uses, controlling diseases, and implementing economic incentives for ecosystem services.