Yamataikoku or Yamaichikoku is the Sino-Japanese name of an ancient country in Wa (Japan) during the late Yayoi period (circa 300 BCE – 300 CE).

The (297 CE) Chinese history Sanguo Zhi first records Yemetaiguo or Yemayiguo as the domain of shaman Queen Himiko (died circa 248 CE).

Generations of Japanese historians, linguists, and archeologists have debated where Yamataikoku was located and whether it was related to Yamato "Japan".