Porrex I was a legendary king of the Britons as accounted by Geoffrey of Monmouth.
He was the son of Gorboduc[1] and his death began a dynastic civil war.
In the final years of Gorboduc's life, Porrex waged war with his brother, Ferrex.
Some time after, his mother, Judon, avenged Porrex's murder of Ferrex and hacked him to pieces in his sleep.
His death sparked a civil war which would not be resolved until the reign of Dunvallo Molmutius.