What they do
The Global Impact Investing Network (GIIN) is the world's largest community dedicated to increasing the scale and effectiveness of impact investing. It publishes annual market surveys, manages the IRIS+ impact measurement system, and provides research, events, and resources for investors seeking both financial returns and measurable social or environmental outcomes.
Why they matter
GIIN defines the field. Its annual surveys are the most-cited source on impact investing market size (now estimated at over $1.1 trillion), and IRIS+ provides the shared language for measuring impact across investments. For anyone entering the impact investing space, GIIN's resources are the starting point for understanding what the market looks like, what returns are realistic, and how to measure outcomes.
How to support
Join as a member, attend the GIIN Investor Forum, or use IRIS+ metrics in your own investment evaluation. Membership tiers range from individual to institutional.
Key project to explore
Start with the Annual Impact Investor Survey. It is the single best snapshot of where the market stands, what asset classes are growing, and what returns investors are actually achieving.