the largest man-made object is the International Space Station (ISS). The ISS is a habitable space station that orbits Earth and serves as a laboratory for scientific research. It is a joint project involving space agencies from the United States, Russia, Europe, Japan, and Canada.
The ISS has been continuously occupied since November 2000 and has a mass of approximately 419,725 kilograms (925,335 pounds). It measures about 109 meters (357 feet) in length, 73 meters (240 feet) in width, and 20 meters (66 feet) in height. The station's size is comparable to that of a football field.
Please note that advancements and new projects may have been developed since I'm not interested in that topic as much as i used to and my answer might be a bit outdated, so there could be newer and larger man-made objects.