At around 3.45 am the 36-year-old woman was on her way through Ludigerplatz in the area of the city's central station when the two men attacked her.
One of the criminals punched the woman in the face and then pulled a knife on her, demanding she hand over all her money.
But rather than be cowed, the woman responded by punching one of her assailants right back. The blow hit home, making the thief bleed from the nose.
Although the woman injured herself in the process, the two men were so shocked that they fled into the night.
Police report that the men are now being sought and are in their early twenties, both between 170cm and 180cm tall.