Sanuki Province (讃岐国, Sanuki-no kuni) was an historical province of Japan on the island of Shikoku, with the same boundaries as modern Kagawa Prefecture. It was sometimes called Sanshū (讃州).
It faced the Inland Sea and bordered on Awa and Iyo Provinces. Across Naruto strait it bordered Awaji Province too. Administratively it was included as a part of Nankaidō. It was settled in the 7th century and originally consisted of the northeastern part of Shikoku and Awaku Islands on the Inland Sea.
Sanuki's ancient capital is believed to have been near modern Sakaide, but has not been discovered. Takamatsu developed as the main seat of the province in the Middle Ages.
In the Classical Period, Sanuki was famous for its associations with the Buddhist monk Kūkai as both his birthplace and the place of his early upbringing. Later, the famed poet Sugawara no Michizane served as governor of the province from 886 to 890 under the Ritsuryō Codes.
In the Sengoku period, Sanuki was ruled by the Miyoshi clan. The Miyoshi were invaded by Chōsokabe clan in Tosa Province and lost Sanuki Province. Finally Chōsokabe lost a battle against Toyotomi Hideyoshi, who rewarded his vassals by assigning Takamatsu Castle to Ikoma Chikamasa , and Sogō Castle to Sogō Masayasu.
In the Edo period, Sanuki was divided into five areas; three han in Takamatsu, Marugame, Tadotsu, the shōgun's direct holding and a part of Tsuyama han whose mainland was on Honshū. Naoshima and Shōdoshima was separated from Bizen Province and merged into Sanuki Province.