It happened at around 7:45 a.m., on the 1800 block of Bryant Street, NE, DC Fire/EMS spokesperson, Pete Piringer said.
A 14-year-old girl was trying to cross the street near a crosswalk.
The bicyclist, who wasn't wearing a helmet, crashed into her and was thrown from his bike, officials said.
The bicyclist was taken to the hospital after the crash and was pronounced dead there, officials said.
The girl suffered only minor injuries, officials said.
A pedestrian always has the right of way - even when crossing "near" a crosswalk, but with the girl being a 14-year old I wouldn't be surprised if either party were ultimately at fault. There are bike lanes on 18th.