In Indo-European linguistics, the term Indo-Hittite (also Indo-Anatolian) refers to Sturtevant's 1926 hypothesis that the Anatolian languages may have split off a Pre-Proto-Indo-European language considerably earlier than the separation of the remaining Indo-European languages. The term may be somewhat confusing, 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.
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 , would be called Proto-Indo-European (PIE). 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.
Traditionally there has been a strong notion among Indo-European linguistics that the Anatolian branch was separated earlier than other branches. Within the Kurgan framework the split time is estimated at roughly 4000 BC.
Some fundamental shared features, such as the aorist category of the verb (which denotes action without reference to duration or completion), with the perfect active particle -s fixed to the stem, link the Anatolian languages closer to the southeastern languages such as Greek and Armenian, and to Tocharian.
Features such as the lack of feminine gender in the declensions of nominals, a division between an "animate" common gender and an "inanimate" neuter gender, a reduced vowel system, a tendency towards a greater simplicity of the case system, a less typical Indo-European vocabulary, and other striking features have been interpreted alternately as archaic debris, as the nucleus for future developments, or just as being caused by prolonged contacts in typologically alien surroundings "en route" or after their arrival in Anatolia. In favor of the Indo-Hittite hypothesis are the very Indo-European agricultural terminology conserved in Anatolia, otherwise considered the cradle of agriculture, and the laryngeal theory that hypothesizes the existence of one or more additional stop or spirant consonants in the Indo-European parent language that has only been attested in Hittite and of which only traces are left outside Anatolian.