Union County is a county located in the U.S. state of Mississippi. It was formed in 1870 from Tippah and Pontotoc counties, and in 1874 a portion of Lee County was added. As of the 2020 census, the population was 27,777. Its county seat is New Albany. According to most sources, the county received its name by being a union of pieces of several large counties, like other Union counties in other states.