Troy is a city in and the county seat of Miami County, Ohio, United States, along the Great Miami River. The population was 26,305 at the 2020 census, making it Miami County's largest city and Ohio's 55th-largest. About 19 miles (31 km) north of Dayton, Troy is part of the Dayton metropolitan area.

Troy was platted around 1807. A post office in Troy has been in operation since 1824.

Troy was one of the cities affected by severe flooding in the Great Flood of 1913.

In 1970, the Troy Historical Society published Troy: The Nineteenth Century, a book on Troy's history by Thomas Bemis Wheeler. The book discusses the city's founding city and the Ohio canal era of the 1800s.

According to the United States Census Bureau, the city has an area of 11.94 square miles (30.92 km), of which 11.72 square miles (30.35 km) is land and 0.22 square miles (0.57 km) is water.

Historical population

Census	Pop.	Note	%±
1810	179		—
1820	293		63.7%
1830	504		72.0%
1840	1,351		168.1%
1850	1,956		44.8%
1860	2,643		35.1%
1870	3,005		13.7%
1880	3,803		26.6%
1890	4,494		18.2%
1900	5,881		30.9%
1910	6,122		4.1%
1920	7,260		18.6%
1930	8,675		19.5%
1940	9,697		11.8%
1950	10,661		9.9%
1960	13,685		28.4%
1970	17,186		25.6%
1980	19,008		10.6%
1990	19,478		2.5%
2000	21,999		12.9%
2010	25,058		13.9%
2020	26,305		5.0%
2021 (est.)	26,432		0.5%
Sources:

As of 2000 the median income for a household in the city was $39,531, and the median income for a family was $46,889. Males had a median income of $35,819 versus $25,536 for females. The per capita income for the city was $19,892. About 6.4% of families and 8.2% of the population were below the poverty line, including 10.8% of those under age 18 and 6.4% of those age 65 or over.

As of the census of 2010, there were 25,058 people, 10,353 households, and 6,600 families residing in the city. The population density was 2,138.1 inhabitants per square mile (825.5/km). There were 11,166 housing units at an average density of 952.7 per square mile (367.8/km). The racial makeup of the city was 90.1% White, 4.2% African American, 0.2% Native American, 2.4% Asian, 0.6% from other races, and 2.4% from two or more races. Hispanic or Latino of any race were 1.8% of the population.

There were 10,353 households, of which 33.1% had children under the age of 18 living with them, 46.1% were married couples living together, 12.9% had a female householder with no husband present, 4.7% had a male householder with no wife present, and 36.3% were non-families. 30.5% of all households were made up of individuals, and 10.6% had someone living alone who was 65 years of age or older. The average household size was 2.38 and the average family size was 2.95.

The median age in the city was 36.9 years. 25.2% of residents were under the age of 18; 7.9% were between the ages of 18 and 24; 28.1% were from 25 to 44; 25.7% were from 45 to 64; and 13.1% were 65 years of age or older. The gender makeup of the city was 48.7% male and 51.3% female.

Troy is home to the Troy-Hayner Cultural Center, a 1914 Romanesque mansion donated to the city by Mary Jane Harter Coleman Hayner. Hayner had been married to William Hayner, founder of a Dayton-based mail-order whiskey business that operated before Prohibition. The Troy-Hayner houses the Hayner Distillery Collection and a variety of works by local artists.

Troy was the location of the Hobart Welded Steel House Company, which might have become influential in U.S. housing if prefabricated houses had become popular after World War II. The firm's homes resemble the better-known Lustron houses of the Columbus, Ohio-based Lustron Corporation (which also failed). Hobart manufactured and built 22 homes, all in Troy, 16 of which survive and are listed on the U.S. National Register of Historic Places.

Other NRHP-listed properties in Troy include four unrelated homes, a tavern, the Miami County Courthouse and Power Station, the 1859 First Presbyterian Church, and the Troy Public Square.

The City of Troy has a statutory form of government, as described in Ohio Revised Code Sections 731 and 733. General statutory law is the form of municipal government if the electorate has not adopted, by vote, one of the other forms. In addition to a council, the electorate chooses a mayor, council president, and three principal administrators (auditor, treasurer, and solicitor). The mayor administers the city's daily operations. Troy also has a service and safety director who reports to and is appointed by the mayor.

The mayor, auditor and law director are elected to four-year terms. The city council is elected to two-year terms in odd-numbered years. The electorate selects the council president, three at-large representatives, and ward representatives 1 through 6. The current mayor and auditor were elected in 2019 and the city council and treasurer were elected in 2021.

The Troy City Police Department is at 124 E. Main Street. It has 38 officers and three civilian employees. The department has three divisions: patrol, detective, and administration. Shawn McKinney is the police chief. The department moved to its current location in 1995.

The Troy Fire Department was established in 1850 when the Troy Hook & Ladder Company and the Troy Bucket Company were organized. The Fire Department of Troy was formally organized in the fall of 1857. The department has three fire stations, 37 firefighter/paramedics, a training lieutenant, 2 assistant chiefs and a fire chief, Matthew D. Simmons. The fire department provides a full complement of services to its citizens with fire/EMS/Community outreach/ specialty rescue services. The Troy Fire Department serves 74.2 square miles with the city and three townships averaging over 5,000 incidents a year.

Troy City Schools operates public schools covering most of the city limits.

School	Type	Grades	Founded
Troy High School	Public	9th-12th	1852
Troy Junior High School	Public	7th-8th	1972
Troy Christian	Private	Pre K-12th	1980
Miami Montessori School	Private	Pre K-6th	1979
The Overfield School	Private	18 months-Kindergarten	1960
Van Cleve Elementary	Public	6th	1914
Concord Elementary	Public	K-5th	1919
Cookson Elementary	Public	K-5th	1963
Forest Elementary	Public	K-5th	1949
Heywood Elementary	Public	K-5th	1931
Hook Elementary	Public	K-5th	1967
Kyle Elementary	Public	K-5th	1950
St. Patrick School	Private	K-8th	1888

A part of Troy is in Miami East Local School District.

The Western Ohio Japanese Language School (オハイオ西部日本語学校 Ohaio Seibu Nihongo Gakkō) is a supplementary weekend Japanese school in unincorporated Miami County, near Troy. It started in April 1988.

Troy is home to the Hobart Institute of Welding Technology, founded in 1930, one of the nation's premier welding schools.

The Troy-Miami County Public Library has three locations in Troy: the main Troy Library, The Local History Library, and the Maker Lab.

The city and surrounding area are served by a daily newspaper based in Troy, Miami Valley Today; the radio station WTJN-LP "POWER 107.1" 107.1 FM; and the magazine Troy Living.

• Ryan Brewer, college football player
• Cris Carter, NFL player
• Nancy J. Currie, engineer, United States Army officer, NASA astronaut
• Pat Darcy, Major League Baseball player
• Casey Black Desantis, First Lady of Florida
• Kris Dielman, NFL player
• Bob Ferguson, NFL player
• Mike Finnigan, keyboard player and vocalist
• Wesley Henderson, architect
• Jack Hewitt, driver and two-time champion in the USAC Silver Crown Series
• Tolbert Lanston, founder of Monotype
• Miss May I, metalcore band
• Richmond Mayo-Smith, economist
• Roger A. McGuire, U.S. Ambassador to Guinea-Bissau
• Sam Milby, Filipino actor
• Heath Murray, Major League Baseball player
• Anne Rudloe, marine biologist
• Peter Shelton, sculptor
• Tim Vogler, NFL player
• Randy Walker, college football coach
• Bradley White, cyclist
• Erin Yenney, professional soccer player

• City website
• Troy Area Chamber of Commerce