Fenner is a town in Madison County, New York, United States. The population was 1,726 at the 2010 census.
According to the United States Census Bureau, the town has a total area of 31.1 square miles (81 km), of which, 31.1 square miles (81 km) of it is land and 0.04 square miles (0.10 km) of it (0.10%) is water.
As of the census of 2000, there were 1,680 people, 607 households, and 455 families residing in the town. The population density was 54.0 people per square mile (20.8/km²). There were 651 housing units at an average density of 20.9 per square mile (8.1/km²). The racial makeup of the town was 98.87% White, 0.18% African American, 0.24% Native American, 0.18% Asian, 0.06% from other races, and 0.48% from two or more races. Hispanic or Latino of any race were 0.36% of the population.
There were 607 households out of which 38.7% had children under the age of 18 living with them, 60.0% were married couples living together, 9.9% had a female householder with no husband present, and 25.0% were non-families. 18.0% of all households were made up of individuals and 4.9% had someone living alone who was 65 years of age or older. The average household size was 2.77 and the average family size was 3.14.
In the town, the population was spread out with 27.7% under the age of 18, 6.5% from 18 to 24, 32.2% from 25 to 44, 24.9% from 45 to 64, and 8.7% who were 65 years of age or older. The median age was 36 years. For every 100 females, there were 100.7 males. For every 100 females age 18 and over, there were 103.4 males.
The median income for a household in the town was $43,846, and the median income for a family was $46,447. Males had a median income of $31,726 versus $25,573 for females. The per capita income for the town was $19,409. About 4.4% of families and 7.1% of the population were below the poverty line, including 8.0% of those under age 18 and 2.8% of those age 65 or over.