Korean kingdom of Silla (57 BC - AD 4). His formal title is Bak Hyeokgeose Geoseogan. (Geoseogan means "King" or "Exalted One.")
He established (in 37 BC) a castle around the Silla capital, Geumseong (modern Kyeongju). In 20 BC a messenger from Mahan demanded that Silla pay tribute, and Bak Hyeokgeose refused to do so.
According to legend, he was born from an egg that a horse from heaven laid.