What was the first major union defeat of general Robert e lee?

The first major defeat of General Robert E. Lee's Army of Northern Virginia came at the Battle of Gettysburg in July 1863. This pivotal battle marked a significant turning point in the Civil War, as Lee's forces were repelled after three days of intense fighting against the Union Army, led by General George G. Meade. The defeat halted Lee's invasion of the North and resulted in substantial Confederate casualties, weakening the South's overall military position.