Stockholm Environment Institute, or SEI, is a non-profit, independent research and policy institute specialising in sustainable development and environmental issues,[1] with seven affiliate offices around the world.

[2] SEI works on climate change, energy systems, water resources, air quality, land-use, sanitation, food security, and trade issues with the aim to shift policy and practice towards sustainability.

The Swedish International Development Cooperation Agency (Sida) is SEI's main donor.

SEI also receives funding from development agencies, governments, NGOs, universities, businesses, and financial institutions.

[5] For example, the Bill and Melinda Gates Foundation also provides funds to SEI in the area of maternal health[5] and in sustainable sanitation.