El Greco's Mary Magdalene in Penitence

El Greco's "Mary Magdalene in Penitence" has a nipple showing. It was painted around 1577 shortly after his arrival in Spain, as part of a series (the others are much more discreet). Some critics believe it is a portrait of his mistress, Jerónima de las Cuevas, with whom he had a son around the same time.

El Greco's
National Museum of Fine Arts, Budapest