The Red River campaign, also known as the Red River expedition, was a major Union offensive campaign in the Trans-Mississippi theater of the American Civil War, which took place from March 10 to May 22, 1864. It was launched through the densely forested gulf coastal plain region between the Red River Valley and central Arkansas towards the end of the war. The offensive was intended to stop Confederate use of the Louisiana port of Shreveport, open an outlet for the sugar and cotton of northern Louisiana, and to split the Confederate lines, allowing the Union to encircle and destroy the Confederate military forces in Louisiana and southern Arkansas. It marked the last major offensive attempted by the Union in the Trans-Mississippi Theater.

The trans-Mississippi theater of the American Civil War was the scene of the major military operations west of the Mississippi River. The area is often thought of as excluding the states and territories bordering the Pacific Ocean, which formed the Pacific coast theater of the American Civil War (1861–1865).