The incident occurred in Karlskoga at a property in the area. Police were called to the scene after reports of a brawl and discovered the woman in a grievious condition on the stairwell.
A 46-year-old man was later arrested and held on probable cause of suspicion of murder.
"They know each other," Lotta Lindblad of the Örebro police told the TT news agency. The authorities would not disclose how the pair knew one another but said that there was an existing relationship.
Police did not reveal the exact details about the murder weapon, stating that it was a sharp object. The crime scene is due to be examined throughout Saturday with police refusing to speculate on what led to the woman being stabbed.