Sofia Kovalevskaya, Russian-Swedish mathematician and physicist (died 1891)

Sofya Vasilyevna Kovalevskaya was a Russian mathematician who made noteworthy contributions to analysis, partial differential equations and mechanics. She was a pioneer for women in mathematics around the world – the first woman to earn a doctorate in mathematics, the first woman appointed to a full professorship in northern Europe and one of the first women to work for a scientific journal as an editor. According to historian of science Ann Hibner Koblitz, Kovalevskaya was "the greatest known woman scientist before the twentieth century".

January 15 is the 15th day of the year in the Gregorian calendar; 350 days remain until the end of the year.