The California Green Building Standards Code, commonly known as CalGreen, is California's first-in-the-nation, statewide green building code. It was implemented to improve public health, safety, and general welfare through enhanced design and construction of buildings. CalGreen sets minimum environmental performance standards for new residential and non-residential buildings throughout California, aiming to reduce greenhouse gas emissions, energy consumption, and water use, while promoting sustainable construction practices and improving indoor air quality.

The code covers a wide range of green building measures, including planning and design, energy efficiency, water efficiency and conservation, material conservation and resource efficiency, and environmental quality. CalGreen is part of the California Building Standards Code and is mandatory for all new construction in California. The requirements are designed to be flexible, allowing builders and designers to choose how they will meet the standards, and they are intended to make green building practices a routine part of construction. CalGreen is updated periodically to incorporate new technologies and methods for sustainable building, reflecting California's ongoing commitment to environmental stewardship and sustainability in the built environment.