西海 is one of the Four Seas (
四海) of Chinese cosmology — north
北海, south
南海, east
东海, west
西海 — each ruled by a Dragon King (
龙王). In 《
西游记》,
西海龙王 敖闰 is the father of the white dragon horse. Historically,
西海 was also used for Qinghai Lake (Han dynasty
西海郡) and in modern Korean Chinese as the name for the Yellow Sea.