Lanier County is a county in the south central portion of the U.S. state of Georgia. At the 2020 census, the population was 9,877. The county seat is Lakeland. It is named after Georgia poet Sidney Lanier.

Lanier County is part of the Valdosta metropolitan area and shares Moody Air Force Base with Lowndes County on its western boundary.

According to the U.S. Census Bureau, the county has an area of 200 square miles (520 km²), of which 185 square miles (480 km²) is land and 15 square miles (39 km²) (7.3%) is water.

The vast majority of Lanier County is in the Alapaha River sub-basin of the Suwannee River basin. Just a narrow section of the western border of the county, northeast and southeast of Ray City, is in the Withlacoochee River sub-basin of the same Suwannee River basin, and a very narrow section of the eastern border of Lanier County is in the Upper Suwannee River sub-basin of the same Suwannee River basin.

The Banks Lake National Wildlife Refuge, established in 1985, hosts approximately 20,000 visitors annually. It provides hiking, fishing, and boating opportunities on more than 4,000 acres (16 km²) of water, Banks Lake marsh, and swamp. The Robert Simpson III Nature Trail, dedicated in August 2001, is in the Lakeland, Georgia city limits on 75 acres (300,000 m²) of pine and hardwood forests. The county is known for its excellent fishing in the Alapaha River, Banks Lake National Wildlife Refuge as well as in its many small lakes.

As of the 2020 United States census, there were 9,877 people, 3,714 households, and 2,536 families residing in the county.

The county's economy has remained rural in nature, but the educational, health and social service sector was the largest employment category in 2006. Factors contributing to this economy include the presence of Moody Air Force Base (shared by adjoining Lowndes County), the several lakes and nature reserve, the hospital, and a large state correctional facility.

The top ten employers in Lanier County are:^{[citation needed]}