The bodies were found by police in a log cabin at an Edersee campsite and officers are treating the case of a suicide pact.
Reportedly there is no sign of foul play and the three women did leave suicide notes.
According to a police statement, the evidence points to the three women meeting and arranging the trip via a social networking site. However, it is unclear if they knew each other before this.
The cabin was rented by one of the women, a 49-year-old from Frankfurt an der Oder, Apparently she rented it on Monday for three people for two nights. (Please note this article does continue after the featured links).
Police said that the campsite owner did not see the women at all during the two day period. However, when he went to check on them on Wednesday afternoon, he saw the carbon monoxide detector on the bathroom door was displaying a warning.
called emergency services to the scene, and when firefighters entered the cabin they found the three women's bodies together in the cabin's bathroom.
No names have been released, but the other women were a 23-year-old from Potsdam, near Berlin, and a 44-year-old from Kassel, a town close by.
Police have not released a motive for the group suicide, although they did say it might be the result of "mental illness."
It is not yet clear whether the prosecutor's office in Marburg will order an autopsy of the bodies.