Nature-based solutions (NBS) are interventions to protect, restore, and sustainably manage natural or modified ecosystems to support both biodiversity and human well-being. This guide explores the benefits of using NBS in a suite of development options to promote sustainable and resource-efficient infrastructure. It includes case studies from Bangladesh, Nepal, the People's Republic of China, the Philippines, and Viet Nam to show how NBS can be mainstreamed in the portfolio of the Asian Development Bank.