Lamar County is part of the Hattiesburg, MS Metropolitan Statistical Area.

It is largely a rural county, except for its northeast quarter.

[3] As of the 2020 United States census, there were 64,222 people, 22,116 households, and 15,584 families residing in the county.

The Mississippi Department of Mental Health operates the South Mississippi State Hospital in unincorporated Lamar County, near Purvis.

[12] School districts include:[13] Former school districts:[14] The county is in the service area of Pearl River Community College.