Leonardo da Vinci, c.1503-19 (Renaissance — universal reference for any modern-art canon). Louvre, Paris.
From Wikipedia
The Mona Lisa is a half-length portrait painting by the Italian artist Leonardo da Vinci. Considered an archetypal masterpiece of the Italian Renaissance, it has been described as "the best known, the most visited, the most written about, the most sung about, [and] the most parodied work of art in the world." The painting's novel qualities include the subject's enigmatic expression, the monumentality of the composition, the subtle modelling of forms, and the atmospheric illusionism.