The chapter introduces the critical role of biodiversity hotspots in global conservation efforts. It highlights that global changes, including habitat loss, invasive species, and anthropogenic climate change, have initiated the sixth mass extinction event in Earth's history. The authors emphasize that limited resources should be allocated to regions most in need of conservation, particularly the 35 biodiversity hotspots identified based on irreplaceability and vulnerability. The chapter reviews the development of these hotspots over the past two decades and discusses past and future conservation efforts. It underscores the importance of these regions as the home of a significant fraction of global biodiversity and as the source of ecosystem services essential for human well-being. The introduction also details the multiple threats to biodiversity, including unsustainable consumption, poverty, agricultural expansion, urbanization, industrial development, overexploitation, invasive species, chemical pollution, and diseases. The chapter further explains the irreversible nature of extinction and the profound consequences of species loss, including the loss of genetic resources, potential medical cures, and cultural and spiritual values. It also highlights how the loss of broader ecosystems can exacerbate human mortality, economic damage, and the spread of diseases.The chapter introduces the critical role of biodiversity hotspots in global conservation efforts. It highlights that global changes, including habitat loss, invasive species, and anthropogenic climate change, have initiated the sixth mass extinction event in Earth's history. The authors emphasize that limited resources should be allocated to regions most in need of conservation, particularly the 35 biodiversity hotspots identified based on irreplaceability and vulnerability. The chapter reviews the development of these hotspots over the past two decades and discusses past and future conservation efforts. It underscores the importance of these regions as the home of a significant fraction of global biodiversity and as the source of ecosystem services essential for human well-being. The introduction also details the multiple threats to biodiversity, including unsustainable consumption, poverty, agricultural expansion, urbanization, industrial development, overexploitation, invasive species, chemical pollution, and diseases. The chapter further explains the irreversible nature of extinction and the profound consequences of species loss, including the loss of genetic resources, potential medical cures, and cultural and spiritual values. It also highlights how the loss of broader ecosystems can exacerbate human mortality, economic damage, and the spread of diseases.