Miller County is a county located in the U.S. state of Missouri. As of the 2020 United States census, the population was 24,722. Its county seat is Tuscumbia. The county was organized February 6, 1837, and named for John Miller, former U.S. Representative and Governor of Missouri.

John Miller was an American publisher, War of 1812 veteran, and politician from Missouri. A Democrat, Miller was the fourth Governor of Missouri before serving three terms in the United States House of Representatives from 1837 to 1843.