A 43-year-old man was gored twice by a bull during celebrations in the southwestern town of Coria, Extremadura on Wednesday, despite standing behind a protective fence.
The bull charged at the crowd, its horns going through the bars of the fence, piercing the man's abdomen and chest.
Graphic footage of the goring has been published in the Spanish media.
The man was rushed to hospital where he died from his injuries.
In a separate incident, an 80-year-old bullfighting aficionado died in hospital on Wednesday in the northeastern town of l'Ampolla, Tarragona after being gored on Monday.
A bull charged at the man during the festival of San Juan, a popular midsummer festival celebrated throughout Spain in honour of Saint John the Baptist, during which bonfires and lit and many towns hold celebratory bull fights.
"The bull gored him with both horns and, although no it didn't hit any vital organs, the man suffered significant blood loss," Francesc Arasa, the mayor of l'Ampolla, told Catalan daily, La Vanguardia.
The man was taken to hospital where he received blood transfusions which ultimately proved unsuccessful and he died on Wednesday.
The Catalan town has cancelled the bull event that was scheduled for Thursday, the final day of the fiesta.