I am inheriting a substantial amount of money and do not wish to give half to my wife; she has a gambling addiction. Am I required, due to our marriage, to share the inheritance from my father with her 50/50?

It depends on what state you are in. However, if you get it and put it in a separate bank account that she isn't on she wouldn't be able to get at it with out going to court. Not saying that it wouldn't hurt your marriage but from what I've heard gambling problems hurt them anyway.

Are you divorcing? If not, then you don't have to just hand over half of any income you get.