Lead is one of a handful of elements which were known from ancient times; thus, it was never formally discovered. In fact, alchemists considered lead the oldest metal.
One of the oldest lead artifacts ever discovered was a Turkish statuette dating from 6500 B.C. The Chinese were minting coins that contained lead by 4000 B.C. Perhaps the most infamous use of lead in ancient times was its use in the Roman Empire's extensive plumbing system. In fact, the very word "plumbing" is etymologically derived from the Latin word for lead: "plumbum." Part of why lead was so well-known and frequently used in ancient times is that it is an exceptionally soft metal, making it much easier to work than iron, gold or copper.