-In ancient times, the area composed by Nagasaki Prefecture and Saga Prefecture was called Hizen Province. The current name dates from the Meiji Restoration. Rice farming culture has prospered here since ancient times, and vestiges can be seen at the ruins of Nabatake in Karatsu and the Yoshinogari site in Yoshinogari.
-From the Kamakura period to the Muromachi period, it is thought that over 100 feudal clans existed. Also exerting great influence during this time was a samurai clan operating along the Genkai Sea called the Matsuratō. Upon entering the Sengoku period, the Ryūzōji clan expanded their control to include all of Hizen and Chikugo Provinces, and part of Higo and Chikuzen Provinces. After the death of daimyō Takanobu Ryūzōji, Naoshige Nabeshima took control of the political situation, and by 1607 all of the Ryūzōji clan's domain was under the control of the Nabeshima clan.
-In the Edo period this area was called the Saga Domain (佐賀藩 Saga-han), and it included three sub-domains: the Hasunoike, Ogi and Kashima Domains. Also within the current borders of Saga Prefecture during this time were the Karatsu Domain (唐津藩 Karatsu-han) and two territories of the Tsushima-Fuchū Domain (対馬府中藩 Tsushimafuchū-han). Saga Domain and its sub-domains continued to be ruled by the Nabeshima clan, its various illegitimate family lineages and members of the former Ryūzōji clan, and politically the area was relatively stable. However, the cost of defending Nagasaki was increasing and, difficult from the start, the financial situation was worsened by the great Kyōhō famine and the Siebold Typhoon of 1828. Nevertheless, due to the large area of reclaimed land from the Ariake Sea arable land was able to increase significantly and by the 1840s the annual koku of Saga Domain increased to about 670,000, twice that of 200 years before.
Around the middle of the 19th century,
Naomasa Nabeshima strove to set right the domain's financial affairs, reduce the number of government officials, and encourage local industry such as Arita porcelain, green tea, and coal. Also, thanks to the proximity of the international port of Nagasaki, new technologies were introduced from overseas, such as the reverberatory furnace and models of steam locomotives.
After the Boshin War, many people from Saga Domain assisted in the Meiji Restoration. In the Meiji era the modernization of coal mines in Kishima and Higashimatsuura districts, among others, progressed bolstered by the construction of railroads.
in Saga. Woodblock print from Tokyo Nichinichi Shimbun
- 6th century BC (end of the Jōmon period): Estimated date of the Nabatake ruins in Karatsu
- 1st century BC (middle of the Yayoi period): Villages flourished at what is now the Yoshinogari site
- 665: After losing the Battle of Baekgang, Kii Castle (in present-day Kiyama) amassed its defenses to protect Dazaifu.
- 733: Hizen Fudoki created.
- 1274: Battle of Bun'ei, the first invasion in the Mongol invasions of Japan
- 1281: Battle of Kōan, the second invasion in the Mongol invasions of Japan
- 1591: Construction of Nagoya Castle. After the Japanese invasions of Korea the castle fell in 1598.
- 1602: Construction of Karatsu Castle and Saga Castle.
- 1607: Control of Saga Domain moved from the Ryūzōji clan to the Nabeshima clan.
- 1771: Nijinomatsubara Uprising
- 1781: Establishment of Kōdōkan, the Saga Han school.
- 1828: Heavy damage from the Siebold Typhoon, deaths estimated at over 10,000.
- 1871, July 14: Abolition of the han system. All of the han became prefectures.
- 1871, November 14: The prefectures of Saga, Hasuike, Ogi, Kashima, Karatsu and part of Tsushima merged to form one prefecture, Imari Prefecture.
- 1872, May 29: Imari Prefecture renamed Saga Prefecture.
- 1874, February: Saga Rebellion.
- 1876, April 18: Incorporation of Mizuma Prefecture.
- 1883: Separation from Nagasaki Prefecture.
- 1889, April 1: The city of Saga is founded.
- 1891: The Kyushu Railroad Nagasaki Line opens, beginning with a section from Tosu to Saga.
- 1895: Opening of railroad from Saga to Takeo.
- 1897: Opening of railroad from Takeo to Haiki.
- 1903: Opening of railroad from Saga to Nishi-Karatsu.
- 1932, January 1: The city of Karatsu is founded.
- 1935: The Japanese National Railways Saga Line opens.
- 1954: During the Great Showa Merger the cities of Tosu, Imari, Takeo, Kashima and Taku are formed. At this point there are 7 cities, 8 districts, 18 towns and 35 villages in Saga Prefecture.
- 1972: With the closing of the Nishiki coal mine, all coal mines in Saga are closed.
- 1975: The Genkai Nuclear Power Plant begins operation.
- 1987: The Japanese National Railways Saga Line closes.
- 1992: The Yoshinogari History Park opens to the public.
- 1998: The Saga Airport opens in Kawasoe, in what is now the city of Saga.
- 2005: As a part of the Great Heisei Merger various municipalities are reorganized.
- 2006: The Great Heisei Merger continues.
- 2007, October 1: The towns of Higashiyoka, Kawasoe and Kubota merge with the city of Saga.
- 2011, March 12: The Kyushu Shinkansen opens.