John Horncastle (or John de Horncastle) was a Bishop of Carlisle. He was elected about 10 January 1353 but was never consecrated as his election was quashed about 26 June 1353.^[1]

• Fryde, E. B.; Greenway, D. E.; Porter, S.; Roy, I. (1996). Handbook of British Chronology (Third revised ed.). Cambridge, UK: Cambridge University Press. ISBN 0-521-56350-X.