Nishio (西尾市) is a Japanese city located at the southern end of the Yahagi River basin, which flows from north to south in central Aichi Prefecture, with mountains such as Mount Sangane to the east, the Yahagi River to the west, and the bay from Mikawa to the south.

Its population is 171.822 inhab., including about 9.909 foreign citizens, of which 3.481 are Brazilians, 437 Peru, 40 Paraguay, 18 Argentina, 20 Americans, 2 Mexico, 2.549 Vietnam, 1.382 Philippines, 699 Chinese, 234 Koreans, 28 Mongolia, 13 Sri Lanka, 106 Nepal, 6 India, 653 Indonesia, (Prefecture data).

The city has a climate characterized by hot, humid summers and relatively mild winters. September is the wettest month. Temperatures are highest in August at around 26.3°C, and lowest in January at around 4.5°C..

After the end of World War II, Nishio attracted many workers from the rural south of Japan and its population increased. In 1953, Nishio became a city with the annexation of the neighboring cities of Heisaka and Terazu and the villages of Fukuchi and Muroba, followed by the villages of Miwa and Meiji in 1955.

On April 1, 2011, the cities of Hazu, Isshiki and Kira (all from Hazu district) were merged into Nishio. The Hazu District was dissolved as a result of this merger.