This guide explores the benefits of using nature-based solutions to promote sustainable and resource-efficient infrastructure. Nature-based solutions are interventions to protect, restore, and sustainably manage natural or modified ecosystems to support both biodiversity and people's well-being. This guide includes case studies from Bangladesh, Nepal, the People's Republic of China, the Philippines, and Viet Nam. It considers challenges and opportunities and shows how nature-based solutions can be mainstreamed in the portfolio of the Asian Development Bank.