The bull run began at 03:00 with the release of the animals through the streets of the town of Fuentesauco in the province of Zamora.
The man, from the Madrid region, was gored in the chest about 90 minutes later and was pronounced dead at the local health centre shortly afterwards, a source at the clinic said.
The bull run was one of several planned as part of a local festival, which began on Friday and was to continue until Tuesday.
All further events scheduled for Saturday were cancelled following the accident.
During a bull run crowds race ahead of a pack of thundering bulls along a course through urban streets to the town bullring where a bullfight is staged.
Spain's most famous annual bull run begins on July 6 during the San Fermin festival in the northeastern town of Pamplona.
A 27-year-old man was killed during last year's San Fermin festival after he tripped and was gored in the neck.