Marietta[4] is a census-designated place (CDP) in Adair County, Oklahoma, United States.

[8] According to the United States Census Bureau, the CDP has a total area of 1.8 square miles (4.7 km2), all land.

The racial makeup of the CDP was 39.13% White, 53.62% Native American, and 7.25% from two or more races.

25.5% of all households were made up of individuals, and 12.8% had someone living alone who was 65 years of age or older.

There were 21.9% of families and 36.4% of the population living below the poverty line, including 68.6% of under eighteens and 40.0% of those over 64.