Mona Lisa

There is also a somewhat crazy theory that the painting depicts Leonardo da Vinci himself.

An excerpt from the article 38 facts about Mona Lisa
Some claimed that Salai (Giovanni Francesco Caprotti), the master's pupil and confidant, or perhaps lover, posed for the portrait. However, the prevailing view was that the master portrayed Lisa Gherardini, the wife of a Florentine merchant.