Union Grove is a town in Marshall County, Alabama, United States, and is included in the Huntsville-Decatur Combined Statistical Area. Union Grove is located approximately 3 miles (5 km) from Guntersville Lake and 6 miles (10 km) from Arab. Electricity service in Union Grove is provided through Arab Electric Cooperative, which comes through the Tennessee Valley Authority. As of the 2010 census, the population of the town was 77.
Union Grove is located at 34°24′0″N 86°26′46″W (34.400088, -86.446049).
According to the U.S. Census Bureau, the town has a total area of 0.6 square miles (1.6 km2), all land.
As of the census of 2000, there were 94 people, 38 households, and 28 families residing in the town. The population density was 165.5 people per square mile (63.7/km2). There were 41 housing units at an average density of 72.2 per square mile (27.8/km2). The racial makeup of the town was 97.87% White, 1.06% Native American and 1.06% Asian.
There were 38 households, out of which 31.6% had children under the age of 18 living with them, 60.5% were married couples living together, 7.9% had a female householder with no husband present, and 26.3% were non-families. 21.1% of all households were made up of individuals, and 13.2% had someone living alone who was 65 years of age or older.