Sergei Anatolyevich Starostin (Cyrillic: Серге́й Анато́льевич Ста́ростин, March 24, 1953 – September 30, 2005) was a Russian historical linguist, 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 of still earlier date. He was also the author of a widely respected reconstruction of Old Chinese.