Marietta is a city in Lac qui Parle County, Minnesota, United States on Minnesota State Highway 40 near the South Dakota border.

[5] According to the United States Census Bureau, the city has a total area of 0.38 square miles (0.98 km2), all land.

There were 101 housing units at an average density of 265.8 per square mile (102.6/km2).

39.0% of all households were made up of individuals, and 18.3% had someone living alone who was 65 years of age or older.

44.2% of all households were made up of individuals, and 25.6% had someone living alone who was 65 years of age or older.

About 14.6% of families and 21.6% of the population were below the poverty line, including 33.3% of those under the age of eighteen and 18.4% of those 65 or over.