The fire in the eighteenth arrondissement, the cause of which is unknown, broke out at around 4:30 am (0230 GMT) and took more than 100 firefighters to contain it.
The eight victims included two who died after they attempted to escape through windows, according to police. A source close to the investigation said two children were among the victims.
The fire started on the ground floor before spreading into the stairwell.
Interior minister Bernard Cazeneuve, present at the scene, said it was “too early to determine the causes of this tragedy”.