German historical linguist known primarily for his scholarship concerning Hittite and the classical languages.

During his academic career, Sommer held professorships at the universities of Basel (1902–09), Rostock (1909–13), Jena (1913–24), Bonn (1924–26), and Munich (1926–51). His most important works include Handbuch der lateinischen Laut- und Formenlehre (1902; “Handbook of Latin Phonology and Morphology”); Zur Geschichte der griechischen Nominalkomposita (1948; “Contributions to a History of the Greek Nominal Compounds”); and a number of significant contributions to Hittite studies, including Die Ahhijava-Urkunden (1932; “The Ahhiyawa Documents”) and Hethiter und Hethitisch (1947; “Hittites and the Hittite Language”).