Komisenian, or Komeši, encompasses heterogeneous of language varieties spoken in and around the Semnan region, situated midway between Tehran and Khorasan. These varieties include Semnani, Biabuneki, Sorxai, Lāsgerdi, Aftari, Sangesari, and Šahmirzādi. While some of these have been recognized by philologists for over a century and a half, their interrelations have yet to receive sufficient scholarly analysis. This study examines these varieties in terms of noun and verb typology, lexis, and diachronic development, proposing their classification within a Sprachbund. Additionally, it explores the relationship between the Komisenian Sprachbund and its historical neighbors—Caspian in the north, Median in the west, and the extinct Gorgāni and Parthian languages in the east—as well as a possible connection of Sangesari with East Iranian. The area's little-documented history is incorporated to support and contextualize the linguistic analysis (This paper is an expanded and updated version of the article initially prepared for the Encyclopaedia Iranica. Publication was halted when the encyclopedia ceased operations in 2023).