Millard County is a county located in the U.S. state of Utah. In 2010, its population was 12,420. It was named for Millard Fillmore, thirteenth President of the United States. Its county seat is Fillmore and the largest city is Delta.

According to the U.S. Census Bureau, the county has a total area of 17,684 km2 (6,828 sq mi). 6,589 miles (17,066 km²) of it is land and 239 square miles (620 km2) of it (3.50%) is water. The Sevier Desert covers much of Millard County, being the seafloor of ancient Lake Bonneville. Near the center of the county lies Sevier Lake, a mostly dry remnant of Lake Bonneville. Mountains rim the area, some of which harbor beautiful forests, contrasting with the deserts below, especially the Pahvant Mountains, which form the county's eastern boundary. Fillmore and other farming communities lie at the base of the Pahvant Mountains. Delta sits several miles from the banks of the Sevier River in the middle of the basin.