Yamatai or Yamatai-koku (邪馬台国) (c. 1st century – c. 3rd century) is the Sino-Japanese name of an ancient country in Wa (Japan) during the late Yayoi period (c. 1,000 BCE – c. 300 CE). The Chinese text Records of the Three Kingdoms first recorded the name as (邪馬臺) or (邪馬壹) followed by the character 國 for "country", describing the place as the domain of Priest-Queen Himiko (卑弥呼). Generations of Japanese historians, linguists, and archeologists have debated where Yamatai was located and whether it was related to the later Yamato (大和国).

Wa is the oldest attested name of Japan. From c. the 2nd century AD Chinese and Korean scribes regularly used the Chinese character 倭; 'submissive'', 'distant'', 'dwarf' to refer to the inhabitants of the Wa kingdoms on Kyushu and those of the ancient Yamato kingdom. In the 8th century, the Japanese replaced the character with 和, wa, 'harmony', 'peace', 'balance'.