Proto-Slavic (wanda aka gajarta PSl., PS.; wanda kuma ake kira Common Slavic ko Common Slavonic ) shine wanda ba a tantance shi ba, wanda aka sake gina shi na duk harsunan Slavic . Yana wakiltar maganganun Slavic kusan daga karni na biyu BC zuwa karni na 6 AD . Kamar yadda yake a yawancin sauran harsunan ƙa’ida, ba a sami tabbataccen rubuce-rubuce ba; malamai sun sake gina harshen ta hanyar yin amfani da hanyar kwatankwacinta ga duk harsunan Slavic da aka tabbatar da kuma yin la'akari da wasu harsunan Indo-Turai .
Saurin haɓaka maganganun Slavic ya faru a lokacin Proto-Slavic lokacin, wanda ya yi daidai da babban fadada yankin masu magana da Slavic. Bambance-bambancen yare ya faru tun da wuri a wannan lokacin, amma gaba ɗaya haɗin kai na harshe da fahimtar juna ya ci gaba har tsawon ƙarni da yawa, zuwa karni na 10 ko kuma daga baya. A wannan lokacin, yawancin sautunan sauti sun bazu ko'ina cikin yankin, galibi iri ɗaya. Wannan ya sa bai dace a kula da ma'anar gargajiya ta proto-harshen a matsayin sabon magabatan gama gari na ƙungiyar harshe, ba tare da bambancin yare ba. (Wannan zai buƙaci magance duk canje-canje na pan-Slavic bayan karni na 6 ko makamancin haka a matsayin wani ɓangare na tarihin daban-daban na harsunan 'ya'ya mata.) Maimakon haka, Slavicists yawanci suna kula da dukan lokacin haɗin kai na harshe daban-daban kamar Slavic Common .
Mutum na iya raba lokacin Proto-Slavic / Common Slavic na haɗin harshe kusan zuwa lokuta uku:
Hukumomi sun bambanta game da waɗanne lokuta ya kamata a haɗa su cikin Proto-Slavic da cikin Slavic gama gari. Harshen da aka kwatanta a cikin wannan labarin gabaɗaya yana nuna tsakiyar lokacin, yawanci ana kiransa Late Proto-Slavic (wani lokaci Slavic gama gari [1] ) kuma galibi ana kwanan wata kusan ƙarni na 7 zuwa 8. Wannan yaren ya kasance ba a tantance shi ba, amma bambance-bambancen ƙarshen zamani, wanda ke wakiltar yaren ƙarshen ƙarni na 9 da ake magana da shi a kusa da Thessaloniki ( Solun ) a Makidoniya, an tabbatar da shi a cikin tsoffin rubutun Slavonic na Coci .