In Indo-European linguistics, the term Indo-Hittite refers to the hypothesis that the Anatolian languages may have split off the Proto-Indo-European language considerably earlier than the separation of the remaining Indo-European languages. The term is somewhat imprecise, as the prefix Indo- does not refer to the Indo-Aryan branch in particular, but is iconic for Indo-European, and the -Hittite part refers to the Anatolian language family as a whole.

It is generally accepted that the Anatolian branch was separated earlier, but while mainstream Indo-European linguistics holds that this may have been a matter of a couple of centuries, maybe roughly 4000 BC in the Kurgan framework, proponents of the Indo-Hittite hypothesis claim the separation may have preceded the spread of the remaining branches by several millennia, possibly as early as 7000 BC. In this context, the proto-language before the split of Anatolian would be called Proto-Indo-Hittite, and the proto-language of the remaining branches, before the next split, presumably of Tocharian, would be called Proto-Indo-European. This is a matter of terminology, though, as the hypothesis does not dispute the ultimate genetic relation of Anatolian with Indo-European, it just means to emphasize the assumed magnitude of temporal separation.