Vincenzo Peruggia
Vincenzo Peruggia is the man who stole the Mona Lisa.
In 1911 when a former Louvre worker walked into the museum, saw that the room holding the Mona Lisa was empty of guards and visitors, took the painting off its pegs, went to a staircase, removed the painting from its frame, and walked out with it under his arm.
The da Vinci went missing for two years until the thief, Vincenzo Peruggia (who became an Italian national hero of sorts), tried to sell it. The buyer went to the police.