Gennady Alekseevich Leonov (1947 - 2018) - Corresponding member of the Russian Academy of Sciences, Foreign Member of the Finnish Academy of Science and Letters, a Council Member of International Federation of Automatic Control, the Highly Cited Mathematician of the Russian Federation, a bearer of many notable awards - passed away on April 23, 2018 after a short battle with a grievous illness. This paper is written in his memory. The authors remember Prof. Leonov as eminent scholar, admired teacher, and unconventional administrator.