Keystone is an unincorporated census-designated place in Hillsborough County, Florida, United States. The population was 14,627 at the 2000 census.
According to the United States Census Bureau, the community has a total area of 39.2 square miles (101.6 km²), of which, 36.1 square miles (93.4 km²) of it is land and 3.2 square miles (8.2 km²) of it (8.05%) is water.
There were 5,160 households out of which 41.7% had children under the age of 18 living with them, 78.2% were married couples living together, 4.7% had a female householder with no husband present, and 15.1% were non-families. 11.1% of all households were made up of individuals and 3.0% had someone living alone who was 65 years of age or older. The average household size was 2.83 and the average family size was 3.08.
In the community the population was spread out with 27.2% under the age of 18, 4.8% from 18 to 24, 33.3% from 25 to 44, 27.1% from 45 to 64, and 7.7% who were 65 years of age or older. The median age was 38 years. For every 100 females there were 100.4 males. For every 100 females age 18 and over, there were 97.9 males.
The median income for a household in the community was $80,677, and the median income for a family was $84,592. Males had a median income of $55,905 versus $37,190 for females. The per capita income for the community was $35,136. About 1.4% of families and 2.4% of the population were below the poverty line, including 2.7% of those under age 18 and 5.4% of those age 65 or over.