This paper studies countries’ productive capabilities relevant to the green economy. It constructs the Green Complexity Index (GCI), which ranks countries in accordance with the number and complexity of green products they export competitively and shows that countries with higher GCI have higher environmental patenting rates, lower CO2 emissions, and more stringent environmental policies. It also looks at each country’s Green Adjacent Possible (GAP), which represents the set of technologically proximate green products that a country could potentially become competitive in.