Killbox 13 is the twelfth full-length studio album by thrash metal band Overkill in 2003. The name stems from the fact that the band considers this to be their thirteenth release because they include the Overkill EP as their first, or that they had released the covers album Coverkill, which would have been their eleventh studio album. "Well, it is the thirteenth, but it's only really the thirteenth for people who followed the band.