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.