Quote from wikipedia:
… The painting was controversial partly because the nude is wearing some small items of clothing such as an orchid in her hair, a bracelet, a ribbon around her neck, and mule slippers, all of which accentuated her nakedness. This modern Venus' body is thin, counter to prevailing standards; thin women were not considered attractive at the time, and the painting's lack of idealism rankled. A fully dressed servant is featured, exploiting the same juxtaposition as in Luncheon on the Grass.
Manet's Olympia was also considered shocking because of the manner in which she acknowledges the viewer. She defiantly looks out as her servant offers flowers from one of her male suitors. Although her hand rests on her leg, hiding her pubic area, the reference to traditional female virtue is ironic; the notion of modesty is notoriously absent in this work. The black cat at the foot of the bed strikes a rebellious note in contrast to that of the Urbino's dog. Manet's uniquely frank (and largely unpopular) depiction of a self-assured prostitute was rejected by the Paris Salon of 1863. At the same time, his notoriety translated to popularity in the French avant-garde community. As with Luncheon on the Grass, the painting raised the issue of prostitution within contemporary France and the roles of women within society.