The San Francisco Fire Department PIO says a quarter of the pier at Fisherman's Wharf "has been lost to the flames."
The flames were visible around 4:17 a.m. local time Saturday morning, as the fire department made sure the pier was fully evacuated.
They made sure the fire was contained to a section of the pier.
The fire caused a partial building collapse on the southern part of the pier, which spread to two buildings and was in danger of spreading to a third.
No word of any injuries or cause of the fire.