Whose theory predicted the existence of black holes from relativity?

Karl Schwarzschild, a German physicist, found an exact solution to Einstein’s general relativity equations while serving during World War I. His 1916 solution described what is now called the Schwarzschild radius, the boundary around a sufficiently compact mass where escape velocity exceeds the speed of light. The modern black-hole concept developed later, but Schwarzschild’s work provided the mathematical foundation. His solution remains one of the most important results in gravitational physics.