Lạc Long Quân (literally "Dragon Lord of Lạc"; also called Hùng Hiền Vương) is considered the second Hùng king of the Hồng Bàng Dynasty of ancient Vietnam (known then as Văn Lang and before that as Xích Quỷ). Quân was the son and sole successor of Kinh Dương Vương (the first Hung king), who ruled over Xích Quỷ. He is thought to have become king in 2793 BC. He is also a significant figure in Vietnamese legend.

In modern day, his life is mixed with many legends. Quân's wife, Âu Cơ, gave birth to a sac containing 100 eggs from which 100 children were born; this is the origin of the story of the 100 Vietnamese family names. One day Lạc Long Quân told Âu Cơ: "I am descended from dragons, you from fairies. We are as incompatible as water is with fire. So we cannot continue in harmony." This said, the husband and wife parted. The man went to the seawards with 50 of their children, while his wife went to the mountainous region with the other half of the clan. The eldest son, who followed his mother, later installed himself as Quân's successor.

Lạc Long Quân's father was Kinh Dương Vương.

The books Đại Việt sử ký toàn thư (from the 15th century) and Lĩnh Nam chích quái ("Wonders plucked from the dust of Linh-nam", from the 14th century) mention the legend with Âu Cơ.

Slaying of Ngư Tinh

During Lạc Long Quân's time, the people of Van Lang was still undeveloped and isolated. In the Eastern sea, there appears a giant fish, called Ngư Tinh (Vietnamese for "fish monster"). This fish has lived for centuries, with the size of its mouth, it can consume a ship with 10 fisherman at the same time. Whenever the fish swim, waves can reach the sky, drown multiple ships, all the people passing through the area were all eaten by the fish. Ngư tinh lives in a big cave under the sea, above the cave is a huge mountain which divide the sea into two areas.

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