Forrest County is a county located in the U.S. state of Mississippi. As of the 2010 census, the population was 74,934. Its county seat and largest city is Hattiesburg. The county was created from Perry County in 1908 and named in honor of Nathan B. Forrest, a Confederate general in the American Civil War and a member of the original Ku Klux Klan. Forrest County is part of the Hattiesburg, MS Metropolitan Statistical Area.