The Battle of Chancellorsville was a major battle of the American Civil War, and the principal engagement of the Chancellorsville Campaign. It was fought from April 30 to May 6, 1863, in Spotsylvania County, Virginia, near the village of Chancellorsville. Two related battles were fought nearby on May 3 in the vicinity of Fredericksburg. The campaign pitted Union Army Maj. Gen. Joseph Hooker's Army of the Potomac against an army less than half its size, Gen. Robert E. Lee's Confederate Army of Northern Virginia. Chancellorsville is known as Lee's "perfect battle" because his risky decision to divide his army in the presence of a much larger enemy force resulted in a significant Confederate victory. The victory, a product of Lee's audacity and Hooker's timid decision making, was tempered by heavy casualties and the mortal wounding of Lt. Gen. Thomas J. "Stonewall" Jackson to friendly fire, a loss that Lee likened to "losing my right arm."

The Chancellorsville Campaign began with the crossing of the Rappahannock River by the Union army on the morning of April 27, 1863. Union cavalry under Maj. Gen. George Stoneman began a long distance raid against Lee's supply lines at about the same time. This operation was completely ineffectual. Crossing the Rapidan River via Germanna and Ely's Fords, the Federal infantry concentrated near Chancellorsville on April 30. Combined with the Union force facing Fredericksburg, Hooker planned a double envelopment, attacking Lee from both his front and rear.