Tradition: Korean Mythology
Alternative names: Isu Yakwoo, Yisu Yakwoo (異獸若牛)
Category: Cow
The Myth
In 799, during the reign of King Soseong of Silla, the governor of Uduju sent a report to the king describing a strange beast that had appeared in the region.
The creature was described as resembling a cow, but it was far larger and stranger than any ordinary cattle. It had a long, massive body, a tail approximately three feet long, no hair, and an unusually long nose. It was seen traveling from Hyeonseongcheon toward Osikyang.
The Silla record gives no name for the creature or any further account of what happened to it. Its description is simply preserved as an “extraordinary beast resembling an ox” (異獸若牛).
Later Korean tradition has sometimes regarded this creature as an early form or possible precursor of the Bulgasari, a famous Korean monster. Its bizarre combination of an ox-like body, hairlessness, enormous size, and elongated nose made it sufficiently unusual to be recorded as an omen-like beast in the Samguk Sagi.
Sources
“이수약우.” 나무위키 (NamuWiki). Accessed August 21, 2026. https://namu.wiki/w/이수약우