Trenton is a city in northeastern Butler County, Ohio, United States, west of Middletown. Originally in Madison Township, it later annexed land in Wayne Township. The population was 11,869 at the 2010 census.
Trenton is located at 39°28′55″N 84°27′34″W (39.481909, -84.459460). The city lies on the west bank of the Great Miami River.
According to the United States Census Bureau, the city has a total area of 4.56 square miles (11.81 km2), all land.
Trenton was originally called Bloomfield, and under the latter name was platted in 1815. Bloomfield was named for Joseph Bloomfield, governor of New Jersey. In 1831, it was discovered that there was already a Bloomfield post office in Ohio, and so the town was renamed after the state capital of New Jersey at Trenton.
Trenton was once a stop on the Cincinnati, Hamilton and Dayton Railway.
As of the census of 2010, there were 11,869 people, 4,160 households, and 3,258 families living in the city. The population density was 2,602.9 inhabitants per square mile (1,005.0/km2). There were 4,454 housing units at an average density of 976.8 per square mile (377.1/km2).