Euclid
Euclid (; – "Eukleídēs", ; fl. 300 BC), sometimes given the name Euclid of Alexandria to distinguish him from Euclides of Megara, was a Greek mathematician, often referred to as the "founder of geometry" or the "father of geometry". He was active in Alexandria during the reign of Ptolemy I (323–283 BC). His "Elements" is one of the most influential works in the history of mathematics, serving as the main textbook for teaching mathematics (especially geometry) from the time of its publication until the late 19th or early 20th century. In the "Elements", Euclid deduced the theorems of what is now called Euclidean geometry from a small set of axioms. Euclid also wrote works on perspective, conic sections, spherical geometry, number theory, and rigor.
Science and technology in Russia
In mathematics Nikolai Lobachevsky, a "Copernicus of Geometry", founded the non-Euclidean geometry playing important role in modern physics. In the 19th century the international recognition was also gained by such mathematicians as Mikhail Ostrogradsky and Sofia Kovalevskaya who was the first major Russian female mathematician, responsible for important original contributions to analysis, differential equations and mechanics, and the first woman appointed to a full professorship in Northern Europe. Yevgraf Fyodorov was a founder of the modern structural crystallography (Fedorov group). At least after such prominent scientist as Chebyshev the Russian mathematical school became one of the most influential ones in the world and was represented by numerous figures greatly contributing to different fields of mathematics, physics and computing sciences. Chebyshev's students included Aleksandr Lyapunov who founded the modern stability theory (lately deeply developed by such scientists as Aleksandr Andronov and Vladimir Arnold), and Andrey Markov who developed the theory of Markov chains, playing a central role in information sciences and modern applied mathematics.
In the beginning of the 20th century Nikolai Zhukovsky and Sergei Chaplygin were among founding fathers of the modern aero- and hydrodynamics and Vladimir Kotelnikov was a pioneer in information theory by independently proposing the fundamental sampling theorem. 
Andrei Kolmogorov, a leading mathematician of the 20th century, developed the foundation of the modern theory of probability and made other key contributions to broadest range of mathematical branches, such as turbulence, mathematical logic, topology, differential equations, set theory, automata theory, information theory, theory of algorithms, dynamical systems, stochastic processes, theory of integration, classical mechanics, mathematical linguistics, mathematical biology and applied sciences. Israel Gelfand is credited with many important discoveries in algebra, topology, mathematical physics and applied sciences. Sergei Sobolev developed the theory of Sobolev space which played an extremely important role in formation of modern mathematical views and introduced the notion of distributions generalizing ideas of Newton and Leibniz.