The Nilfgaardian harpy is a steel sword in The Witcher 2: Assassins of Kings. It may be obtained as a random drop from sentries guarding the entrance to the Nilfgaardian Quarter in Chapter 3.

On Roche's Path, this sword can be found in the Nilfgaardian Camp immediately after saving Triss (should you decide to save Triss instead of Anaïs). After leaving the dungeon Triss was held in, run through the large door leading to the exit. In the next area, run forward and you should see a ladder on the other side of a fallen wall. Turn right and the Harpy will be in a chest among other items.