Georgia Southern is also moving its football program from the NCAA Division I Football Championship Subdivision to the Bowl Subdivision. The Eagles have been very successful on the FCS level, winning six national titles since 1985 and 10 conference championships since 1993.
"This is a milestone day for Georgia Southern University, and we are very excited to be joining the Sun Belt conference," Georgia Southern President Brooks Keel said.
"This decision was made with the long-term interest of our university in mind. The Sun Belt will provide our student-athletes with an outstanding opportunity to compete at a highest level and we are excited to contribute to the conference's success both on and off the field."
Appalachian State is expected to make a similar move to the Sun Belt, it was reported.
Both schools would have to wait until the 2015 football season to be eligible to be selected for a bowl appearance. Georgia Southern will retain its previously announced 2013 football schedule but won't be eligible for the FCS playoffs.
The Sun Belt currently has 11 members, although five have said they are leaving. Seven other schools, counting Appalachian State and Georgia Southern, are joining the Sun Belt in the next two years.