GeSe2–Ga2Se3–KX (X=I, Br, or Cl) chalcohalide glasses are synthesized, and their optical properties and thermo-mechanical properties are investigated. A structural model is put forward to elucidate the interesting compositional dependences of the short-wavelength absorption edge (λs) and glass transition temperature (Tg). These glasses are transparent in the red-light region in addition to the 3–5 and 8–14 μm atmospheric windows. Most of their Tg exceed 300°C, and they also present good thermal stability. These properties make them attractive materials for infrared optics.