The city-states of central and southern Korea during the so-called Proto–Three Kingdoms period had been grouped into three confederacies called Samhan.

Silla began as Saro-guk, a statelet within the twelve-member confederacy called Jinhan.

Saro-guk consists of six villages and six clans.

According to Korean records, Silla was founded by King Park Hyeokgeose in 57 BCE, around present-day Gyeongju.

Hyeokgeose is said to have been hatched from an egg laid from a white horse, and when he turned thirteen, six clans submitted to him as king and established Saro (or Seona).

He is also the progenitor of the Park clan, now one of the most common family names in Korea.

The earliest recording of this date is found in the Samguk Sagi, a twelfth-century Korean history.

Current archaeological evidence indicates that while a polity may have been established even earlier than this in the Gyeongju region, it is too early to call it a kingdom.

The author of the Samguk Sagi, Kim Bu-sik, probably attempted to legitimize Silla rule by giving it historical seniority over its rival kingdoms Baekje and Goguryeo.