Thomas Royen (born July 6, 1947 in Frankfurt am Main) is a retired German professor of statistics who has been affiliated with the University of Applied Sciences Bingen.
Royen came to prominence in the spring of 2017 for a relatively simple proof for the Gaussian Correlation Inequality (GCI), a conjecture that originated in the 1950s, which he had published three years earlier without much recognition.
A proof of this conjecture, which lies at the intersection of geometry, probability theory and statistics, had eluded top experts for decades.