Union Star is a city in northwest DeKalb County, Missouri, United States, along the Third Fork of the Platte River.

[5] The city most likely was named for the fact a large share of the local residents were pro-Union during the Civil War.

Union Star is 20 miles from Saint Joseph and Exit 50 on Interstate 29, on U.S. Highway 169.

According to the United States Census Bureau, the city has a total area of 0.26 square miles (0.67 km2), all land.

27.4% of all households were made up of individuals, and 17.1% had someone living alone who was 65 years of age or older.

35.5% of all households were made up of individuals, and 19.7% had someone living alone who was 65 years of age or older.