The life and work of Aleksandr A. Chuprov (1874-1926), the most important Russian and continental statistician at the time, is described here for the first time. The book is based on archive sources from Moscow and contains many passages from Chuprov's correspondence with Anderson, Bortkiewicz, Markov and Slutsky. Above all, Chuprov strove to unite the then existing currents of statistical thinking (English school and continental direction). He was extremely successful and made great contributions to the emergence of mathematical statistics.