Since the beginning of the 21st century, the boundaries between humans, animals, and the natural world have become increasingly blurred. The recent global outbreaks of infectious diseases, ecosystem changes triggered by climate change, labor shortages in rural and agricultural areas, and the growing frequency of encounters between humans and wildlife—these are not isolated issues, but interconnected, compound risks that influence one another. Addressing such multifaceted challenges within a single sector has clear limitations. This is where the concept of One Health has emerged. One Health provides a comprehensive framework that encompasses not only human health but also the health of animals, plants, and ecosystems, promoting interdisciplinary and cross-sectoral collaboration. In this article, we will explore the historical background that gave rise to the One Health concept, real-world practices and initiatives based on it, and its relevance to pressing issues in Japan—such as the increasing human–bear conflicts and the controversies surrounding large-scale solar power (mega-solar) developments.