Euhemerus (330-260 BC) was a Greek philosopher and was the best known of the classical writers to rationalise mythology as history and who gave his name to this method of rationalising. Comparable views have also been identified in the writings of a number of early authors including. Xenophanes, Herodotus, Hecataeus of Abdera and Ephorus.
Among his contentions was one that identified Zeus as a king who died on Crete(b). Euhemerism particularly saw the ‘gods’ in Greek mythology as glorified manifestations of early kings and cultural heroes from a distant past. Support for this idea has waxed and waned over the centuries, with fewer followers today. An interesting paper(a) by Professor William Harrison on this subject is worth reading.
>Another Greek writer about whom very little is known was Palaephatus, although there is evidence that he wrote in Athens in the late 4th century BC and was also famous for rationalising myths(c).<
(a) See: https://web.archive.org/web/20190501113737/https://wayback.archive-it.org/6670/20161201173100/http:/community.middlebury.edu/~harris/
(b) Zeus Is Dead: Euhemerus and Crete, S. Spyridakis, The Classical Journal, Vol. 63, No. 8, May, 1968, pp. 337-340.