Evolutionary insights are fundamental to biodiversity conservation, as they reveal the ultimate causes that drive adaptation and persistence of populations, species, and ecosystems over time. In recent decades, the field of conservation biology has expanded to incorporate species' evolutionary histories, adaptive mechanisms, rapid evolution, and interactions with ecosystems to better understand the complexities of species' persistence in the long run. To address this growing recognition that conservation is inherently an evolutionary question, we propose "conservation evolutionary biology" as a new subdiscipline of conservation biology. It aims to explore the past, present, and future of biodiversity from an evolutionary viewpoint, revealing how species and ecosystems respond and adapt to changing environments, thereby to inform science-based, future-oriented conservation strategies to sustain biodiversity in a rapidly changing world. This article highlights the principles, research focus, methodologies, and practices of this emerging field, encouraging further exploration to address the conservation challenges of our time within a unified framework.