St. Dennis is a former census-designated place in western Jefferson County, Kentucky, United States.

[1] According to the United States Census Bureau, the CDP has a total area of 6.8 km2 (2.6 sq mi), all land.

As of the census[3] of 2000, there were 9,177 people, 3,725 households, and 2,559 families residing in the CDP.

The racial makeup of the CDP was 63.75% White, 33.92% African American, 0.29% Native American, 0.32% Asian, 0.01% Pacific Islander, 0.48% from other races, and 1.23% from two or more races.

27.5% of all households were made up of individuals, and 10.5% had someone living alone who was 65 years of age or older.