La belle ferronniere is a portrait of a lady, usually attributed to Leonardo da Vinci. It is also known as Portrait of an Unknown Woman. The painting's title, applied as early as the seventeenth century, identifying the sitter as the wife or daughter of an ironmonger (a ferronniere), was said to be discreetly alluding to a reputed mistress of Francis I, of France, married to a certain Le Ferron. Leonardo da Vinci (1452-1519), Italian artist and polymath.