Catholic Encyclopedia
The Four Crowned Martyrs are actually two groups, with a total of nine or ten martyrs. The first five were masons or sculptors in Pannonia, martyred in 305. The second was a group of four martyrs, names unknown. They have been venerated since the fourth century and share a feast day on 8 November.
For All the Saints
Katherine I. Rabenstein attempts to sort out the claimants to the title of the Four Crowned Martyrs.