Nishio (西尾市, Nishio-shi) is a city located in Aichi Prefecture, in the Chūbu region of Japan.

Nishio is situated on the northern coast of Mikawa Bay on the Pacific Ocean in southern Aichi Prefecture.

Shell mounds dating to the late Japanese Paleolithic period which have been found in what is today the town center also point to fish and seafood as important early local produce.

In Hazu, a shrine from the Nara period is evidence of an early cultural connection to the Japanese capital at the time.

Early in the Meiji period, with the establishment of the modern municipalities system, Nishio was proclaimed a village in Hazu District in 1871.

After the end of World War II, Nishio attracted many workers from the rural south of Japan and its population increased.

Nishio has a mayor-council form of government with a directly elected mayor and a unicameral city legislature of 30 members.

In terms of national politics, the city is part of Aichi District 12 of the lower house of the Diet of Japan.

Its foreign residents section offers assistance in Chinese, Korean, Portuguese, Spanish and English.

The Clean Center recycling plant in Kenjoda accepts all kinds of garbage, including bulky items and hazardous waste.

Nishio is a regional commercial center and fishing port, with a mixed economy of light manufacturing and agriculture.

Public libraries and community centers are maintained in central Nishio, Hazu, Isshiki, Kira and Terazu.

In 2006, the city entered the Guinness Book of Records for having the largest simultaneous tea ceremony in the world at any one time with 14,718 participants.