At least four people have been killed in the accident, the German police tell AFP.
The accident occurred around 18.10 near the city of Riedlingen in the state of Baden–Württemberg. At least three people have been injured, says a spokesperson for the authority.
100 people are said to have been on board the regional express train during the derailment.
Images from the scene show train cars with major damage and one of them has overturned.
It is still unclear what caused the derailment, but a resident in the area tells the German Bild that there was "a severe thunderstorm when the accident occurred".
Germany's Chancellor Friedrich Merz says he is shocked after the incident.
"We mourn the victims. I send my condolences to their families", he writes in a post on X.
