As of the census2 of 2000, there were 26,523 people, 9,842 households, and 7,273 families residing in the county. The population density was 23/km² (59/mi²). There were 10,482 housing units at an average density of 9/km² (24/mi²). The racial makeup of the county was 98.30% White, 0.05% Black or African American, 0.35% Native American, 0.36% Asian, 0.00% Pacific Islander, 0.54% from other races, and 0.41% from two or more races. 0.93% of the population were Hispanic or Latino of any race.

There were 9,842 households out of which 36.70% had children under the age of 18 living with them, 61.30% were married couples living together, 8.70% had a female householder with no husband present, and 26.10% were non-families. 22.70% of all households were made up of individuals and 10.70% had someone living alone who was 65 years of age or older. The average household size was 2.66 and the average family size was 3.13. The median income for a household in the county was $41,426, and the median income for a family was $47,019. Males had a median income of $34,055 versus $23,610 for females. The per capita income for the county was $17,559. 7.50% of the population and 6.30% of families were below the poverty line. 8.00% of those under the age of 18 and 8.70% of those 65 and older were living below the poverty line.

Neighboring areas include Franklin County, Dearborn County, Ohio County, Switzerland County, Jefferson County, Jennings County, and Decatur County. The cities and towns of Ripley County are Batesville, Friendship, Holton, Milan, Napoleon, Osgood, Sunman, and Versailles.