The Brownsville affair, or the Brownsville raid, was an incident of racial discrimination that occurred in 1906 in the southwestern United States due to resentment by white residents of Brownsville, Texas, of the Buffalo Soldiers, black soldiers in a segregated unit stationed at nearby Fort Brown. When a white bartender was killed and a white police officer wounded by gunshots one night, townspeople accused the members of the African-American 25th Infantry Regiment. Although their commanders said the soldiers had been in the barracks all night, evidence was allegedly planted against the men.As a result of a United States Army Inspector General's investigation, President Theodore Roosevelt ordered the discharge without honor of 167 soldiers of the 25th Infantry Regiment, costing them pensions and preventing them from ever serving in federal civil service jobs. The case aroused national outrage in both black and white communities. After more investigation, several of the men were allowed to re-enlist.

Following publication of a history of the affair in the early 1970s, a renewed military investigation exonerated the discharged black troops. The government pardoned the men in 1972 and restored their records to show honorable discharges, but it did not provide retroactive compensation to them or their descendants. Only one man had survived to that time; Congress passed an act to provide him with a tax-free pension. The other soldiers who had been expelled all received posthumous honorable discharges.

The Twenty-fifth United States Infantry Regiment was one of the racially segregated units of the United States Army known as Buffalo Soldiers. The 25th served from 1866 to 1957, seeing action in the American Indian Wars, Spanish–American War, Philippine–American War and World War II.