The fire broke out about 3:45 on Wednesday morning at Ascension Manor, a senior apartment building on the 900 block of North Seventh Street.
When firefighters arrived they were told the fire was inside a seventh floor apartment.
They raced to the unit and quickly extinguished the flames, then discovered the body of a man in his 70s.
The man's name has not yet been released.
The fire marshall is on the scene, to try to determine the cause.
Firefighters managed to contain the flames to the one apartment, but a nearby unit has smoke and water damage.
