Sonchis was the elderly Egyptian priest of Sais, who, according to Plutarch(a), related to Solon the story of Atlantis as recorded in their temple. These conversations took place around 590 BC. Additionally, Plutarch records that Solon also spoke with Psenophis a priest of Heliopolis.
Lewis Spence notes that Clement of Alexandria also gave Sonchis as the name of the Egyptian priest who related to Pythagoras details of the science of the Egyptians.
Another name suggested by Paulo Riven is that of Udja-Hor-res-ne (Wedjahor-Resne) which might relate to another priest or an alternative name for Sonchis. This person was not only a priest and physician but also an admiral. A headless statue of Udja-Hor-res-ne is to be found in the Vatican Museum. I would urge caution regarding this identification.