Ōmachi (大町市, Ōmachi-shi) is a city located in Nagano Prefecture, Japan.

It merged with the neighboring villages of Taira, Tokiwa and Yashiro on July 1, 1954 to form the city of Ōmachi.

Per Japanese census data,[4] the population of Ōmachi has been declining over the past 40 years.

Ōmachi has a mayor-council form of government with a directly elected mayor and a unicameral city legislature of 16 members.

Ōmachi is a regional commercial center and a producer of aluminum, cotton thread and rice.