Olive Branch is an unincorporated community in Alexander County, Illinois, United States. Although it is unincorporated, it has a post office, with the ZIP code of 62969. The population of the ZIP Code Tabulation Area (ZCTA) for ZIP Code 62969 was 879 at the 2000 census. Olive Branch is part of the Cape Girardeau–Jackson, MO-IL Metropolitan Statistical Area.