Olinto De Pretto (26 April 1857 – 16 March 1921) was an Italian industrialist and geologist from Schio, Vicenza.
There is evidence that De Pretto may have been the first person to derive the energy–mass-equivalence
E
=
m
c
2
{\displaystyle E=mc^{2}}
, generally attributed to Albert Einstein.
De Pretto suggested that radioactive decay of uranium and thorium was an example of mass transforming into energy.