The Colfax massacre, sometimes referred to by the euphemism Colfax riot, occurred on Easter Sunday, April 13, 1873, in Colfax, Louisiana, the parish seat of Grant Parish. An estimated 62-153 black militia men were killed while surrendering to a mob of former Confederate soldiers and members of the Ku Klux Klan. Three white men also died in the confrontation.

In the wake of the contested 1872 election for governor of Louisiana and local offices, a group of white men armed with rifles and a small cannon overpowered black freedmen and state militia occupying the Grant Parish courthouse in Colfax. Most of the freedmen were killed after surrendering, and nearly another 50 were killed later that night after being held as prisoners for several hours. Estimates of the number of dead have varied over the years, ranging from 62 to 153; three whites died but the number of black victims was difficult to determine because many bodies were thrown into the Red River or removed for burial, possibly at mass graves.Historian Eric Foner described the massacre as the worst instance of racial violence during Reconstruction. In Louisiana, it had the most fatalities of any of the numerous violent events following the disputed gubernatorial contest in 1872 between Republicans and Democrats. Foner wrote, "...every election [in Louisiana] between 1868 and 1876 was marked by rampant violence and pervasive fraud." Although the Fusionist-dominated state "returning board," which ruled on vote validity, initially declared John McEnery and his Democratic slate the winners, the board eventually split, with a faction declaring Republican William P. Kellogg the victor. A Republican federal judge in New Orleans ruled that the Republican-majority legislature be seated.Federal prosecution and conviction of a few perpetrators at Colfax under the Enforcement Acts was appealed to the Supreme Court. In a key case, the court ruled in United States v. Cruikshank (1876) that protections of the Fourteenth Amendment did not apply to the actions of individuals, but only to the actions of state governments. After this ruling, the federal government could no longer use the Enforcement Act of 1870 to prosecute actions by paramilitary groups such as the White League, which had chapters forming across Louisiana beginning in 1874. Intimidation, murders, and black voter suppression by such paramilitary groups were instrumental to the Democratic Party regaining political control in the state legislature by the late 1870s.

In the late 20th and early 21st centuries, historians have paid renewed attention to the events at Colfax and the resulting Supreme Court case, and their meaning in American history, including contemporary history.