The Lady with the Veil, Alexander Roslin
Zoomable image on Google Art Project, downloadable high resolution file on Wikimedia Commons, original is in the Nationalmuseum Sweden.
Roslin, a Swedish Rococo portrait painter who spent much of his career in France, used his wife, pastel painter Marie-Suzanne Giroust, as his model for this enigmatic and alluringly provocative portrait. It is his best known work, recognized by many who don’t know the name of the artist himself.
You can see another portrayal of her, along with a self portrait by Roslin, here.