Olive Branch is an unincorporated census-designated place in Alexander County, Illinois, United States.

Olive Branch is part of the Cape Girardeau–Jackson, MO-IL Metropolitan Statistical Area.

[4] As of the 2020 census[6] there were 650 people, 217 households, and 161 families residing in the CDP.

There were 330 housing units at an average density of 34.91 per square mile (13.48/km2).

24.88% of all households were made up of individuals, and 20.28% had someone living alone who was 65 years of age or older.