[ Leonhard Euler Leonhard Paul Euler (pronounced [ˈɔɪlɐ] in German, /ˈɔɪlɚ/ YU -lər in English; 15 April, 1707 – 18 September, 1783) was a pioneering Swiss mathematician and physicist who spent most of his life in Russia and Germany . Euler made important discoveries in fields as diverse as calculus and