The longest structure ever built by humans is the Great Wall of China. It stretches over approximately 13,000 miles (about 21,196 kilometers) and was constructed intermittently from the Spring and Autumn period through to the Ming dynasty over more than 2,000 years. The Great Wall served primarily as a defensive barrier and stands as the longest military structure in the world.
Another notable mention is the Walls of Benin, which at one time were considered among the longest man-made structures, reaching around 16,000 kilometers according to some sources, but the Great Wall of China is more widely recognized and documented as the longest continuous structure.
Thus, the Great Wall of China holds the definitive record for the longest structure ever built by humans.
