Christofilis Maggidis, who heads excavations at the site in southern Greece, said Tuesday that the chunk of worked limestone was found two years ago, in a streambed under the imposing citadel.
He told a press conference in Athens that the royal throne was among sections of the hilltop palace that collapsed during an earthquake around 1200 B.C.
Greek Culture Ministry officials have distanced themselves from the identification, citing a separate study that ruled the chunk to be part of a stone basin.
But Maggidis said the find was unmistakably made for sitting on, and would have been no use for holding liquids as it is made of porous stone.
Throne image from and additional information available at: World Archaeology May 2016.