Ōta River is a 103 kilometer-(64 mile-) long river as its main stream from Mt. Kanmuri (冠山 Kanmuri-yama) (1,339m). The Ōta River is the major river that flows through Hiroshima Prefecture and empties into the Seto Inland Sea. The river descends through steep topography, with hydroelectric power plants situated along the river.
Ōta River has numerous of tributaries around the upper streams and join with Tone River and Misasa River in Asakita-ku, Hiroshima and branch into Kyōbashi River, Tenma River and Motoyasu River in the delta area of Hiroshima. Ōta River made the Hiroshima Delta. It is spanned by the Aioi Bridge, the aiming point for the Atomic bombing of Hiroshima.
Ōta River runs through Kitahiroshima, Akiota, Akitakata, Higashihiroshima and Hiroshima. The size of a catchment area is 1,710km²