The Battle of St. John's Bluff was fought from October 1–3, 1862, between Union and Confederate forces in Duval County, Florida, during the American Civil War.

Early in the war, in order to stop the movement of Union Navy ships up the St. Johns River, Confederate Brigadier General Joseph Finnegan established an artillery battery on St. Johns Bluff, on the south side of the river 18 miles downstream from Jacksonville, Florida.

With few resources Finnegan managed to fortify St. Johns Bluff where Confederate troops used slave labor to construct defenses.

The Union dispatched over 800 soldiers to Florida from South Carolina to take the bluff expecting it to be a challenging obstacle.

The Confederate threat in North Florida no longer prevented Federals from seizing the St. Johns River and Jacksonville.