What was Einstein's 1st invention

His first invention was relativity.

“He was convinced of the merits of general relativity because it allowed for a more accurate prediction of planetary orbits around the sun, which fell short in Isaac Newton’s theory, and for a more expansive, nuanced explanation of how gravitational forces worked.
Einstein's assertions were affirmed via observations and measurements by British astronomers Sir Frank Dyson and Sir Arthur Eddington during the 1919 solar eclipse, and thus a global science icon was born. “