This c. 1571 painting by François Clouet now titled "A Lady in Her Bath" has traditionally been considered to be a portrait of Diane de Poitiers. It hangs in the National Gallery of Art in Washington, DC.
"Diane de Poitiers (3 September 1499 – 25 April 1566) was a French noblewoman and a prominent courtier at the courts of king Francis I and his son, King Henry II of France. She became notorious as King Henry's favourite. Because of this, she wielded much influence and power at the French Court, which continued until Henry was mortally wounded in a tournament accident. It was during this tournament that his lance wore her favour (ribbon) rather than his wife's.But modern scholarship has turned against the identification of this bather as Diane de Pointiers.
The subject of paintings by François Clouet as well other anonymous painters, Diane was also immortalised in a statue by Jean Goujon." -- Wikipedia
"Only two signed paintings by François Clouet are known to exist, of which this, generally regarded as one of the great masterpieces of the French Renaissance art, is one. The subject, shown seated in her bath, traditionally was believed to be the famous beauty, Diane de Poitiers (1499-1566), a favourite of Henry II and virtual ruler of France. However, this identification is now rejected, and the dating, placed either in the 1550s or around 1571 is debated. Diane do Poitiers. Other candidates for the identity of the sitter are Mary Stuart (Mary, Queen of Scots) and Marie Touchet, mistress to Charles IX.
This is the classic portrayal of a Royal mistress in her official role, cool, beautiful, aloof, bejewelled even in her bath, accompanied by the strappings of her state: fine rooms, a noble child in the arms of its leering, accomplice-nurse, the sly Love-child stealing the fruits, the flower of passion in her hand.
Regarding the several influences, Titian's influence has been cited. The motif of the servant in the background performing a domestic chore is seen as deriving from the Venus of Urbino." -- Web Gallery of Art
The National Gallery of Art says this about this portrait
"François Clouet, the son of a Netherlandish artist, became court painter to the French kings Francis I, Henry II and Charles IX. In this Renaissance portrait Clouet has depicted a female nude, whose identity is unknown, at her bath. The bather is seated in her tub, which is lined with a white cloth and hung on both sides with regal crimson curtains to ward off the cold. Her left hand draws back the bath sheet revealing the artist's name inscribed below, while her right hand rests on a covered board that displays a sumptuously rendered still life. Slightly behind the bather a young boy reaches for some grapes as a smiling wet nurse suckles a baby. In the background, a maid is seen holding a metal pitcher of bath water as more water is heated in the fireplace. The allusion is to a happy, healthy home.The composition of this piece begins with the naked breasts of the subject and continues through the head of a child in spiral fashion to the wet nurse.
The masklike symmetry of the bather's face makes exact identification difficult; scholars have suggested that her aristocratic features indicate that she is one of several royal mistresses. It is possible that the nude, a Venus type, represents ideal beauty rather than a specific individual. The contrast of the smoothly rendered nude figure to the intricate surface details of the fruit, draperies, and jewelry, presents a union of Flemish and Italian motifs that characterized French courtly art of the sixteenth century."
and ultimately to the jug held by a servant.