Emperor Ōjin (応神天皇, Ōjin Tennō) is the fifteenth emperor of Japan to appear on the traditional list of emperors.

No certain date can be assigned for this emperor's reign, but it appears that he ruled the country from the mid to late fourth century.

Tradition, however, assigns him dates of life from 210 to 310 and places his reign from 270 onwards, although none of these dates have been proven otherwise.

He is the first historical emperor of Japan, his predecessors being now considered as belonging to the legend of the country. He himself was deified as Hachiman Daimyōjin, protector of warriors, and the Minamoto clan made him their patron kami.

Emperor Ōjin's Legend

According to the Kojiki and Nihon shoki, Ōjin was the fourth son of Emperor Chūai and his wife Jingū.

Ōjin is considered by historians to be a "legendary emperor" of the fifth century. The reign of Emperor Kinmei (c. 509-571), the 29th emperor  is the first to which contemporary historiography can assign verifiable dates;

however, the classically accepted names and dates of the early emperors are considered "traditional" until the reign of Emperor Kanmu (737-806), the 50th ruler of the Yamato dynasty.

Since Chūai died before his son was born, Jingū became regent and controlled the country. Ōjin was born in 210 in Tsukushi upon his mother's return from the invasion of Korea and was named Prince Hondawake.

His mother remained regent and he did not succeed her until 270. During his reign, immigrants of Chinese origin from the Korean peninsula, such as Wani whose family came from the Chinese commandery of Lelang, and Prince Yuzuki no Kimi descended from the Chinese Qin dynasty, came to Japan.

Ōjin, who sent Takenouchi no Sukune to conquer Kyūshū, lived in two palaces in Osaka and was assigned the kofun of Habikino, near Osaka, as his tomb.

The Nihon ōdai ichiran posits that Ōjin Tennō lived 110 years, and reigned 41.

At the construction of his first temple, Ōsai-no-miya, eight white pavilions (Yawata) are said to have "descended from the sky," which is why he was equated with the deity Hachiman Daimyōjin, whose name also reads Yahata-no-kami, the god of eight banners.

Some historians equate him with one of the "five kings of Wa".

Emperor Ōjin's Tomb

Historians have identified the tomb of Emperor Ōjin as the Konda Gobyōyama Kofun burial mound, located in the city of Habikino (Osaka Prefecture). In 1848, a number of objects were excavated from a satellite tomb of the mound, the Konda Maruyama Kofun, registered today as National Treasures and kept at the Konda Hachimangu Shrine.

They include two gilded bronze pommels decorated with dragon motifs, a bridle fragment with a mirror-like plate, a deer antler sword hilt, horse ornaments, iron arrowheads, and cuirass fragments.

The equine ornaments show, according to historians, a clear continental influence, and in particular the style of the three Yan kingdoms in northeast China during the so-called Sixteen Kingdoms period (348-436).

This tends to demonstrate the existence of relations between the mainland and the archipelago in the fourth and fifth centuries.

The mausoleum of this monarch is formally named and maintained by the Imperial Agency as Eega no Mofushi no oka no misasagi.