IStalzer told her son that she had been attacked by several men in the street and managed to drag herself home where she was found.
A newly elected mayor was found with multiple life-threatening stab wounds in western Germany, the daily paper Bild reported on Tuesday.
Iris Stalzer was elected as mayor of Herdecke on 28 September. She is a member of the centre-left Social Democratic Party (SPD), the junior party in Germany's conservative-led national government.
German news agency dpa, citing unidentified security sources, reported that she was found by her son at home with life-threatening injuries and had several stabbing wounds to her stomach and back.
She told her son that she had been attacked by several men in the street and managed to drag herself home.
Police said only that there was a large operation underway in Herdecke.
Germany’s Chancellor Friedrich Merz wrote on social media that "we fear for the life of mayor-elect Iris Stalzer and hope for her full recovery.”
The leader of the Social Democrats' parliamentary group in Berlin, Matthias Miersch, told reporters that "we heard a few minutes ago that newly elected mayor Iris Stalzer was stabbed in Herdecke." He said that "we hope that she survives this terrible act."
"We can't say anything at the moment about the background," he added.
Stalzer, who beat a candidate from Merz's centre-right Christian Democrats (CDU) in a runoff vote to win election, is due to take office on 1 November.
Herdecke is a town of about 23,000 people in western Germany's Ruhr region, between the cities of Hagen and Dortmund.
Stalzer's website says she is 57 and married with two teenage children. It says she has spent almost her whole life in Herdecke and has worked as a lawyer specialising in labour law.
The motive for the attack remains unclear but the incident is likely to spark memories of the murder of conservative local government president Walter Luebcke in 2019.
A supporter of then Chancellor Angela Merkel's refugee policy, he was shot dead by a far-right activist on the terrace of his home.
This is a developing story and our journalists are working on further updates.