Ulsan belonged to Jinhan in the Samhan times.
Its name was later changed to Hakok, and it was incorporated into Imran-gun in the 16th year of King Gyeongdeok, the 35th King of Silla.
During the reign of King Taejo in the Goryeo Dynasty, Hago, Dongjin, and Woopoonghyun were integrated, and were collectively promoted as Heungryobu. During the reign of King Hyeonjong, the 16th King in the Goryeo Dynasty, its name was changed to Ulju.