Nagasaki borders Saga Prefecture on the east, and is otherwise surrounded by water, including Ariake Bay, the Tsushima Straits, and the East China Sea.
On October 1, 2005, city of Hirado and the towns of Ikitsuki and Tabira and the village of Oshima (all from Kitamatsuura District) merged to form the city of Hirado.
On October 11, 2005, the towns of Aino, Azuma, Chidiwa, Kunimi, Mizuho, Obama and Minamikushiyama (all from Minamitakaki District) merged to form the new city of Unzen.