The man was found by another cyclist around 6 a.m. in the northwest corner of Coyote Point Park near the Peninsula Humane Society, San Mateo County Parks and Recreation Director Dave Holland said.
A preliminary investigation determined the man crashed into a 3- to 4-foot tall wood fence sometime between 5 and 6 a.m., according to Holland.
The man, who was wearing a helmet when he crashed, was pronounced dead at the scene.
"What caused him to ride into the fence we don't know," Holland said, but added authorities speculated the man might have had a medical condition.
Thousands of Bay Area residents were expected to ride their bicycles to work today in celebration of the region's Bike to Work Day.
The crash is Coyote Point Park's first reported fatal bicycle