A dynamic material flow model was developed to simulate the evolution of global aluminum stocks in geological reserve and anthropogenic reservoir from 1900 to 2010 on a country level. The contemporary global aluminum stock in use (0.6 Gt or 90 kg/capita) has reached about 10% of that in known bauxite reserves and represents an embodied energy amount that is equivalent to three-quarters of the present global annual electricity consumption. The largest proportions of in-use stock are located in the U.S. (28%), China (15%), Japan (7%), and Germany (6%) and in sectors of building and construction (40%) and transportation (27%). Industrialized countries have shown similar patterns of aluminum in-use stock growth: once the per-capita stocks have reached a threshold level of 50 kg, they kept a near linear annual growth of 5-10 kg/capita; no clear signs of saturation can yet be observed. The present aluminum in-use stocks vary widely across countries: approximately 100-600 kg/capita in industrialized countries and below 100 kg/capita in developing countries. The growing global aluminum in-use stock has significant implications on future aluminum demand and provides important recycling opportunities that will be critical for greenhouse gas emissions mitigation in the aluminum industry in the coming decades.