The World Inequality Study is a report published by the World Inequality Lab at the Paris School of Economics that gives estimates of worldwide income and wealth inequality based on the most recent World Inequality Database results (WID). WID, commonly known as WID.world, is an open-source database that is part of a global collaborative project including over a hundred scholars from five continents.

It contains talks on prospective future academic research and also information relevant to public debates and policies on economic inequality. The inaugural report, World Inequality Report 2018, was issued on December 14, 2017, at the Paris School of Economics during the first WID.world Conference and was prepared by Lucas Chancel, Facundo Alvaredo, Gabriel Zucman, Thomas Piketty, and Emmanuel Saez, using WID data. The 300-page analysis warns that the divide between affluent and poor has widened since 1980 throughout the world. In Europe, the development in inequality was more gradual, but it was quick in North America and Asia. Income inequality did not rise in the Middle East, Africa, or Brazil, but remained extremely high.