The Battle of Poison Spring, also known as the Poison Spring massacre, was fought in Ouachita County, Arkansas, on April 18, 1864, as part of the Camden Expedition, during the American Civil War. A Union force commanded by Major General Frederick Steele had moved from Little Rock, Arkansas, in support of Major General Nathaniel Banks's movement along the Red River towards Shreveport, Louisiana. Steele's objective was also Shreveport, and his men occupied Camden, Arkansas. After Banks was defeated at the battles of Mansfield and Pleasant Hill, Steele was isolated in Arkansas. Short on supplies, Steele sent a detachment commanded by Colonel James M. Williams on April 17 to forage for 5,000 bushels of corn that were reported to be in the area.

The Camden Expedition was the final campaign conducted by the Union Army in Arkansas during the Civil War. The offensive was designed to cooperate with Major-General Nathaniel P. Banks' movement against Shreveport.