Eldorado is a village in Preble County, Ohio, United States. The population was 509 at the 2010 census. It is part of the Dayton Metropolitan Statistical Area.
Eldorado is located at 39°54′14″N 84°40′33″W (39.903889, -84.675781).
According to the United States Census Bureau, the village has a total area of 0.23 square miles (0.60 km2), all land.
As of the census of 2010, there were 509 people, 196 households, and 141 families living in the village. The population density was 2,213.0 inhabitants per square mile (854.4/km2). There were 223 housing units at an average density of 969.6 per square mile (374.4/km2). The racial makeup of the village was 99.0% White, 0.6% Asian, 0.2% from other races, and 0.2% from two or more races. Hispanic or Latino of any race were 0.2% of the population.
There were 196 households, of which 35.7% had children under the age of 18 living with them, 55.1% were married couples living together, 9.7% had a female householder with no husband present, 7.1% had a male householder with no wife present, and 28.1% were non-families. 20.9% of all households were made up of individuals, and 8.1% had someone living alone who was 65 years of age or older.