Quirino Francesco Valentino Majorana (28 October 1871^[1] – 31 July 1957) was an Italian experimental physicist who investigated a wide range of phenomena during his long career as professor of physics at the Universities of Rome, Turin (1916–1921), and Bologna (1921–1934).

Majorana performed a long series of very sensitive gravity shielding experiments from 1918 to 1922, which have never been reproduced. Majorana's experiments determined that mercury or lead around a suspended lead sphere acted as a screen and slightly decreased the Earth's gravitational pull.^[2] No attempts have been made to reproduce his results using the same experimental techniques. Other researchers have concluded from other data that if gravitational absorption does exist, it must be at least five orders of magnitude smaller than Majorana's experiments suggest.^[3]

Critical of Albert Einstein's relativity theory, Majorana tried to disprove Einstein’s postulate on the constancy of the speed of light, but he failed, and therefore his experiments confirmed Einstein's postulate.^{[4] [5]} Majorana also confirmed Isaac Newton’s law of universal gravitation to high precision.^[6][7][8]

His later work at Bologna was influenced by correspondence with his nephew Ettore Majorana (1906–1938), another physicist.^[9][10]