Karl Schwarzschild
The simplest black hole solution was obtained by the German Karl Schwarzschild.
In fact, he obtained exact solutions to Einstein's new equations of
general relativity even before Einstein did, and obtained them while he was on the Russian front in the First
World War. He also did important work in other areas of physics such as optics.
His remarkable career was cut
short at age 43. He died shortly after returning home
in 1916 of a disease that he contracted while in Russia.