Sergei Anatolyevich Starostin was a Russian historical linguist and philologist, perhaps best known for his reconstructions of hypothetical proto-languages, including his work on the controversial Altaic theory, the formulation of the Dené–Caucasian hypothesis, and the proposal of a Borean language family of still earlier date. None of his proposed macrofamilies have seen wide-scale acceptance in the linguistic community and are mostly seen as implausible.