is a river in Fukushima Prefecture, Tochigi Prefecture and Ibaraki Prefecture, Japan. It rises at the northern slope of Mount Yamizo, where the border of these three prefectures is located, and flows into Pacific Ocean at Hitachi and Tokai in Ibaraki Prefecture. It has a length of and a drainage area of , and is designated as a Class A river.
The name Kuji is thought to be derived from the phonetically similar word for whale (kujira in Japanese). ', one of the existent fudoki, states: "There were a hill that resembled a whale [kujira]. Then the emperor named the land Kuji." The river is known for ayu fishing. In 2006 it had the second largest catch of ayu in Japan after the Naka River, which is also located in Ibaraki Prefecture. A fishing weir (梠yana) for tourists is installed along the river in Daigo. Fukuroda Falls are located on the Taki River (æ»Âå· Takigawa), which is one of its tributary rivers. One midwinter phenomenon is called ', in which frazil ice that is formed at the bottom floats to the surface. Distribution of freshwater fish like salvelinus and masu salmon captured in Fukushima Prefecture was restricted after the Fukushima Daiichi nuclear disaster in 2011, though restrictions on Kuji River fish has been gradually removed.
Kuji River originates from the northern slope of Mount Yamizo, where the border of Fukushima Prefecture, Tochigi Prefecture and Ibaraki Prefecture is located. It initially flows to the northeast in Tanagura, Fukushima and then changes the flow direction to the sounth in the town. The dividing ridges of Abukuma River and Kuji River are relatively low, and it is considered that Kuji River captured the course of Abukuma River in the past. It flows along a narrow plain between and and into Ibaraki Prefecture. In Ibaraki Prefecture it flows through Daigo, Hitachiomiya and flows finally into Pacific Ocean at the border of Hitachi and Tokai. While the mainstream of the river flows through Fukushima Prefecture and Ibaraki Prefecture, some tributaries flow through Otawara in Tochigi Prefecture (former Kurobane), which is located in the southwest of Mt.Yamizo.
The approximately 80% of the basin consists of mountains and hills, and the rest consists of plateaus and plains. In the downstream basin there is Naka Plateau (é£çÂÂå°å°) between Naka River and Kuji River, which is a fluvial terrace formed by the erosion and deposition by the two rivers.
In the basin there are five cities, five towns and two villages, which are listed below. the population of the basin is approximately 200,000.