This chapter introduces the field of industrial ecology, defining its key topics, approaches, and tools. Industrial ecology focuses on product design and manufacturing processes, viewing firms as agents for environmental improvement due to their technological expertise. It is both industrial and ecological, drawing on non-human ecosystems as models for industrial activity and examining the broader ecosystems that support human technological activity. The field emphasizes a systems perspective, using life cycle analysis, materials and energy flow analysis, and systems modeling to avoid narrow, partial analyses. Technological change is a key theme, with ecodesign and eco-efficiency as prominent elements. The role of businesses is highlighted, as they are seen as important agents for environmental improvement and can play a more active role in environmental policy. Dematerialization and eco-efficiency are also discussed, focusing on reducing resource consumption and environmental releases. The chapter concludes by addressing the goals and boundaries of industrial ecology, noting that it aims to improve and maintain environmental quality while optimizing resource use. The field's normative and positive aspects, as well as the tension between transformative and incremental change, are explored.This chapter introduces the field of industrial ecology, defining its key topics, approaches, and tools. Industrial ecology focuses on product design and manufacturing processes, viewing firms as agents for environmental improvement due to their technological expertise. It is both industrial and ecological, drawing on non-human ecosystems as models for industrial activity and examining the broader ecosystems that support human technological activity. The field emphasizes a systems perspective, using life cycle analysis, materials and energy flow analysis, and systems modeling to avoid narrow, partial analyses. Technological change is a key theme, with ecodesign and eco-efficiency as prominent elements. The role of businesses is highlighted, as they are seen as important agents for environmental improvement and can play a more active role in environmental policy. Dematerialization and eco-efficiency are also discussed, focusing on reducing resource consumption and environmental releases. The chapter concludes by addressing the goals and boundaries of industrial ecology, noting that it aims to improve and maintain environmental quality while optimizing resource use. The field's normative and positive aspects, as well as the tension between transformative and incremental change, are explored.