The connection between the Jewish religion and ethnicity is a cause for many a debates (e.g. this one happening right now). But it is undeniable that while the Jewish ethnic identity, is not the same thing as the practice of the Jewish religion, it is very very closely linked, so much so that to a casual observer the two may appear to be one and the same. Even to the point that there is not consensus on how to refer to the ethnicity without referring to the religion.
My question is, are there any other religions that have a link that strong to a particular ethnicity? I don’t mean countries where there is an established religion that doesn’t recognize as citizens people who aren’t that religion (which in turn may be linked to an ethnicity or language).