Police and emergency medical services responded to a call just after midnight at an apartment building located on Broadview Avenue, near Mortimer Avenue.
A woman was found suffering from a single stab wound. She was rushed to hospital, but did not survive.
Police have a man in custody.
The suspect was arrested at the scene. He was later charged with second-degree murder.
Police say they have not released the name of the accused, or the victim, as they are still trying to reach next of kin.
Anyone with information is asked to contact investigators at 416-808-7400, or to call Crime Stoppers at 416-222-8477.