Radical Reconstruction refers to the post-Civil War plan for the South as envisioned and implemented by the Radical Republicans in Congress. Therefore, it is also referred to as Congressional Reconstruction. Presidents Lincoln and Johnson wanted Reconstruction to be a way to peacefully reunite the country. They favored giving amnesty to most former rebels and restoring most property rights. Many members of Congress, however, wanted to completely remake the South, punish the Confederates, and create a society where former slaves were empowered.

The election of 1866 led to enough Republicans winning congressional seats that the party gained a veto-proof majority. This allowed Republicans to pass a number of significant Reconstruction-related acts the following year. This included the Military Reconstruction Act, which divided the former Confederacy into zones of military occupation. Congress also required Southern states to adopt the Fourteenth and Fifteenth Amendments, which protected the rights of former slaves.

To protect nearly four million former slaves, Radical Reconstructionists established the Freedman's Bureau. This federal agency provided education, healthcare, job assistance, and housing to many. The Army was also used to protect the rights of Black people at the polls. Numerous Black Americans were elected to political office during this period.

Many White Southerners fought back against the continued presence of federal soldiers in the South and objected to the newly-gained liberties of the Black population. After some time, many Northerners grew tired or apathetic to the seemingly never-ending task of remaking the South as a place safe for Black Americans. Radical Reconstruction came to an end after 1876 when Rutheford B. Hayes made a deal with Southern Democrats. In exchange for certifying his victory in the contested presidential election, Hayes promised to withdraw federal troops from the South, bringing Radical Reconstruction to an end the following year.