The Confederate States of America (CSA), commonly referred to as the Confederate States or the Confederacy, was an unrecognized breakaway herrenvolk republic in the Southern United States that existed from February 8, 1861, to May 9, 1865. The Confederacy comprised U.S. states that declared secession and warred against the United States during the American Civil War. They were South Carolina, Mississippi, Florida, Alabama, Georgia, Louisiana, Texas, Virginia, Arkansas, Tennessee, and North Carolina.

The Confederacy was formed on February 8, 1861, by seven slave states: South Carolina, Mississippi, Florida, Alabama, Georgia, Louisiana, and Texas. All seven were in the Deep South region of the United States, whose economy was heavily dependent upon agriculture—particularly cotton—and a plantation system that relied upon enslaved Americans of African descent for labor. Convinced that white supremacy and slavery were threatened by the November 1860 election of Abraham Lincoln to the U.S. presidency on a platform that opposed the expansion of slavery into the western territories, the seven slave states seceded from the United States, with the loyal states becoming known as the Union during the ensuing American Civil War. In the Cornerstone Speech, Confederate Vice President Alexander H. Stephens described its ideology as centrally based "upon the great truth that the negro is not equal to the white man; that slavery, subordination to the superior race, is his natural and normal condition."

Before Lincoln took office on March 4, 1861, a provisional Confederate government was established on February 8, 1861. It was considered illegal by the United States federal government, and Northerners thought of the Confederates as traitors. After war began in April, four slave states of the Upper South—Virginia, Arkansas, Tennessee, and North Carolina—also joined the Confederacy. Four slave states — Delaware, Maryland, Kentucky, and Missouri — remained in the Union and became known as the border states. The Confederacy nevertheless recognized two of them — Missouri and Kentucky — as members, accepting rump state assembly declarations of secession as authorization for full delegations of representatives and senators in the Confederate Congress; In the early part of the war the Confederacy controlled and governed more than half of Kentucky and the southern portion of Missouri, but they were never substantially controlled by Confederate forces after 1862, despite the efforts of Confederate shadow governments, which were eventually defeated and expelled from both states. The Union rejected the claims of secession as illegitimate, while the Confederacy fully recognized them.

The Civil War began on April 12, 1861, when the Confederates attacked Fort Sumter, a Union fort in the harbor of Charleston, South Carolina. No foreign government ever recognized the Confederacy as an independent country, although Great Britain and France granted it belligerent status, which allowed Confederate agents to contract with private concerns for weapons and other supplies. By 1865, the Confederacy's civilian government dissolved into chaos: the Confederate States Congress adjourned sine die, effectively ceasing to exist as a legislative body on March 18. After four years of heavy fighting, nearly all Confederate land and naval forces either surrendered or otherwise ceased hostilities by May 1865. The war lacked a clean end, with Confederate forces surrendering or disbanding sporadically throughout most of 1865. The most significant capitulation was Confederate general Robert E. Lee's surrender to Ulysses S. Grant at Appomattox on April 9, after which any doubt about the war's outcome or the Confederacy's survival was extinguished, although another large army under Confederate general Joseph E. Johnston did not formally surrender to William T. Sherman until April 26. Contemporaneously, President Lincoln was assassinated by Confederate sympathizer John Wilkes Booth on April 15. Confederate President Jefferson Davis's administration declared the Confederacy dissolved on May 5, and acknowledged in later writings that the Confederacy "disappeared" in 1865. On May 9, 1865, U.S. president Andrew Johnson officially called an end to the armed resistance in the South.

After the war, Confederate states were readmitted to the Congress during the Reconstruction era, after each ratified the 13th Amendment to the U.S. Constitution outlawing slavery. Lost Cause ideology, an idealized view of the Confederacy valiantly fighting for a just cause, emerged in the decades after the war among former Confederate generals and politicians, as well as organizations such as the United Daughters of the Confederacy and the Sons of Confederate Veterans. Intense periods of Lost Cause activity developed around the turn of the 20th century, and during the civil rights movement of the 1950s and 1960s in reaction to growing support for racial equality. Advocates sought to ensure future generations of Southern whites would continue to support white supremacist policies such as the Jim Crow laws through activities such as building Confederate monuments and influencing textbooks to write on Lost Cause ideology. The modern display of Confederate flags primarily started during the 1948 presidential election, when the battle flag was used by the Dixiecrats. During the Civil Rights Movement, segregationists used it for demonstrations.