Warren County is a county located in the U.S. state of Mississippi. Its western border is formed by the Mississippi River. As of the 2020 census, the population was 44,722. Its county seat is Vicksburg. Established by legislative act of December 22, 1809, Warren County is named for American Revolutionary War officer Joseph Warren.

Vicksburg is a historic city in Warren County, Mississippi, United States. It is the county seat. The population was 21,573 at the 2020 census. Located on a high bluff on the east bank of the Mississippi River across from Louisiana, Vicksburg was built by French colonists in 1719. The outpost withstood an attack from the native Natchez people. It was incorporated as Vicksburg in 1825 after Methodist missionary Newitt Vick. The area that is now Vicksburg was long occupied by the Natchez Native Americans as part of their historical territory along the Mississippi. The first Europeans who settled the area were French colonists who built Fort Saint Pierre in 1719 on the high bluffs overlooking the Yazoo River at present-day Redwood. They conducted fur trading with the Natchez and others, and started plantations. During the American Civil War, it was a key Confederate river-port, and its July 1863 surrender to Ulysses S. Grant, along with the concurrent Battle of Gettysburg, marked the turning-point of the war.