Ao Jun, the Dragon King of the West Sea, is one of the four dragon kings of the Chinese Pantheon. Each rules one of the four seas that surround the earth, inhabiting a marvelous palace of crystal deep beneath the waves. Each has a cabinet of ministers made up of the greatest members of each species of animal in that sea. They also control armies of fish, crabs, and crayfish who watch over their domains and police the seabed.
More importantly to humans, the dragon kings are responsible for bringing rain to the sections of land that border their domains. They can only do this under the orders of the Celestial Emperor, Yu-Huang-Shang-Ti. The dragon kings also oversee their smaller relatives, the Chiang Lung, the dragons in charge of individual rivers, waterways, and lakes.
In their true forms, the dragon kings are huge serpent-bodied dragons similar to the chiang lung. They can also take the forms of human men or women. The dragon kings have no avatars, and dwell in person on the Prime Material Plane.
The other dragon kings are Ao Kuang, Ao Ch'in, and Ao Shun. The dragon kings are similar to Ryujin of the Japanese Pantheon.
Source: Legends & Lore ( 1990), page 84.
External link: Ao Jun on Wikipedia.