What items could cause a complete loss of oil pressure in my 2001 Dodge Ram truck?

What items could cause a complete loss of oil pressure in my 2001 Dodge Ram truck?
You haven't given enough info, do you have an oil pressure gauge and is it reading o, is there oil in the crankcase, is the truck running ok??

As long as you much oil at all in it, it can only be a few things. If the engine runs and sounds normal, it is the oil pressure gage. If it makes all kinds of racket, and maybe won't start, likely the oil pump drive is busted. Possibly the oil pump intake blocked.