Authorities say Sidney Kang, 31, was attacked by two other inmates at about 10:00 a.m. Thursday in a maximum-security recreational yard at Kern Valley State Prison in Delano.
He was treated for his injuries at the prison but died a short time later.
Two weapons made by inmates were found and the death is being investigated as a homicide.
Prison officials believe that Kang was attacked by fellow inmates Anthony Ramirez and Michael Caldera.
Kang was serving 14 years for assault in Los Angeles County.