Originally from Cologne, Niehoff had been in intensive care since last Friday in a hospital in Hamburg's Altona district. She died on Thursday after suffering cardiovascular problems at the age of 63.
“I had everything. All walks of life. They were whiny, begging, demanding, mean. Well-behaved, sweet, rich, poor, young, old. I don't know what I'm still missing,” she told newspaper Die Welt in one of her last big interviews last summer.
Just last year the former prostitute moved back to Hamburg's red-light district after her she closed down her guesthouse in Germany's Eifel region.
Niehoff lived through drugs, child prostitution and desperate attempts to get out of the sex trade. She grew up in an orphanage before slipping into prostitution, when she married a brothel owner, who committed suicide ten years later.
She worked as a prostitute in Munich and Hamburg and had her own brothel before she began to push for the legalisation of prostitution in Germany in the 1980s. She then became a social worker to help women to get off the street.
“I have seen so many people die,” she said of her time working in Hamburg's St. Pauli district.