Limestone County is a county of the U.S. state of Alabama, and is included in the Huntsville Metropolitan Area.It is also included in the merged Huntsville-Decatur Metro Area. Its name comes from Limestone Creek, a local stream. In 2000, the population was 65,676. In 2008, the United States Census Bureau estimated the county's population at 76,135. Its county seat is Athens.

Limestone County comprises the Thirty-Ninth Judicial Circuit of Alabama. The Thirty-Ninth Judicial Circuit was created in the early 1980s when Limestone County broke away from Morgan County to form its own circuit.The Thirty-Ninth Judicial Circuit has two circuit judges and two district judges. The two circuit judges are Judge James W. Woodroof and Judge Robert M. Baker. The two district judges are Judge Jeanne W. Anderson and Judge Jerry L. Batts.The current District Attorney is Kristi A. Valls.