Southeastern Ceremonial Complex, abbreviated S.E.C.C., is the name given by modern scholars to the regional stylistic similarity of artifacts, iconography, ceremonies, and mythology of the Mississippian culture. It coincided with their adoption of maize agriculture and chiefdom-level complex social organization from 1200 to 1650 CE.

The Mississippian culture was a Native American civilization that flourished in what is now the Midwestern, Eastern, and Southeastern United States from approximately 800 to 1600, varying regionally. It was known for building large, earthen platform mounds, and often other shaped mounds as well. It was composed of a series of urban settlements and satellite villages linked together by loose trading networks. The largest city was Cahokia, believed to be a major religious center located in what is present-day southern Illinois.