How do you say your wife in French?

Teh French use "madame" to address a married woman. You can also and very correctly, use "madame" to address an unmarried woman when her marital status is irrelevant (for instance the lady selling your bread at the bakery). In fact it is usual to do so unless the person is so young that it is obvious that she cannot possibly be married, in which case you would use "mademoiselle".