SO (Heb. sô’). The name of a king of Egypt, mentioned in 2Kgs.17.4 as king in the days of Ahaz king of Judah and Hoshea king of Israel. Hoshea made an alliance with So, bringing down the wrath of Assyria on Israel (2Kgs.17.5). It is difficult to identify him. He is either the king mentioned in Herodotus by the name of Sabaeo, or he is to be identified with Sib’e who in 720 b.c., because of his alliance with the king of Gaza, had to fight with Sargon, by whom he was defeated.