was a province of Japan in the area of modern Chiba Prefecture. The province was located in the middle of the Bà Âsà  Peninsula, whose name takes its first kanji from the name of Awa Province and its second from Kazusa and Shimà Âsa provinces. Its abbreviated form name was or . The borders of Kazusa Province were defined by Shimà Âsa Province to the north, the Pacific Ocean to the east, Awa Province to the south, and Tokyo Bay to the west.
Kazusa was classified as one of the provinces of the Tà Âkaidà Â. Under the Engishiki classification system, Kazusa was ranked as a "great country" (大å½) and a "far country" in relation to its distance from the capital (é å½). Along with Kà Âzuke and Hitachi, it was originally one of the provinces where an imperial prince was nominally assigned as governor.
Kazusa was originally part of a larger territory known as , which was divided into "upper" and âÂÂlowerâ portions (i.e. Kazusa and Shimà Âsa) during the reign of Emperor Kà Âtoku (645âÂÂ654). It was well known to the Imperial Court in Nara -period Japan for its fertile lands, and is mentioned in Nara period records as having supplied hemp to the Court. Kazusa was divided into 15 counties, of which the four counties comprising the district of Awa were separated in 718 into a separate province. The exact location of the capital of Kazusa is not precisely known, but is believed to have been somewhere within the borders of the modern city of Ichihara, Chiba. The ruins of the kokubun-ji, or provincial temple, of Kazusa has been located in the Sà Âza district of Ichihara. The kokubun-ji was first excavated in 1949, and is on a plateau above the Yà Ârà  River in close proximity to Tokyo Bay. The site is protected as a Designated Historic Site of Japan. However, the Ichinomiya of Kazusa Province is the Tamasaki Shrine in what is now the town of Ichinomiya, Chiba, on the opposite coast of the province.
During the Heian period, the province was divided into numerous shà Âen controlled by local samurai clans, primarily the Chiba clan, which sided with Minamoto no Yoritomo in the Genpei War. During the Kamakura period, much of the province was under the control of the Ashikaga clan. By the early Muromachi period, the area was a highly contested region highly fragmented by various samurai clans. However, by the Sengoku period, the Satomi clan had gained control over much of Awa, Kazusa and Shimà Âsa provinces.
The Satomi provided only lukewarm support to Toyotomi Hideyoshi during the Battle of Odawara against the Later Hà Âjà  clan and were subsequently deprived of their holdings in Kazusa and Shimà Âsa. After the installation of Tokugawa Ieyasu in Edo, Kazusa became part of the Tokugawa clan holdings, and Tokugawa hereditary retainer Honda Tadakatsu was promoted to daimyà  of à Âtaki Domain (50,000 koku).
During the Edo period, several small domains were created within the borders of Kazusa, most of which continued to be retained as tenryà  territory owned directly by the shà Âgun and administered by various hatamoto. The entire province had an assessed revenue of 425,080 koku.
Following the Boshin War, Jà Âzai Domain was abolished for its opposition to the Meiji Restoration, and six minor domains were created for daimyà  dispossessed with the creation of Sunpu Domain for the ex-shà Âgun Tokugawa Yoshinobu. These various domains and tenryà  territories were transformed into short-lived prefectures in July 1871 by the abolition of the han system, and the entire territory of Kazusa Province became part of the new Chiba Prefecture on June 15, 1873.
The area of former Kazusa Province was organized into nine districts by the Meiji period cadastral reforms, later reduced to five: