John Michell first proposed that stars could collapse into objects with gravity too strong for light to escape.
In 1783, Michell presented this idea to the Royal Society. Using Newtonian gravity, he reasoned that a sufficiently massive and compact star could have an escape velocity greater than the speed of light. He called such an object a “dark star.”
Michell’s calculation was not a black-hole theory in the modern relativistic sense, because general relativity did not yet exist. However, the central insight—that light could be unable to escape from an extremely compact object—anticipated the event horizon.
Pierre-Simon Laplace independently described a similar possibility in 1796. A common mix-up is crediting Einstein with inventing the concept; Einstein developed general relativity, while Michell’s dark-star argument came more than a century earlier.