Union County lies in the northeastern portion of Mississippi and contains approximately 415 square miles. It is bordered on the north by Benton and Tippah Counties, on the east by Prentiss and Lee Counties, on the south by Pontotoc County, and on the west by Lafayette and Marshall Counties.

New Albany, Union County’s largest municipality and County Seat, is centrally located in the county. New Albany is approximately 75 miles from Memphis, Tennessee; 165 miles from Birmingham, Alabama; 185 miles from Jackson, Mississippi; and 200 miles from Nashville, Tennessee.

Union County is traversed by Future Interstate 22 (U.S. Highway 78) in a northwest/southeast direction, Miss. Highway 15 in a north/south direction, and Miss. Highway 30 in a roughly east/west direction. Miss. Highway 178 (old U.S. Highway 78) essentially parallels Future Interstate 22 and runs through downtown New Albany. Union County is 29 miles east-west and 16 miles north-south at its maximum dimensions.