The Etymological Dictionary of Slavic Languages: Proto-Slavic Lexical Stock (Russian: Этимологический словарь славянских языков. Праславянский лексический фонд / Etimologicheskiy slovar' slavyanskikh yazykov. Praslavyanskiy leksicheskiy fond, abbreviated ESSJa / Russian: ЭССЯ) is an etymological dictionary of the reconstructed Proto-Slavic lexicon. It has been continuously published since 1974 until present, in 43 volumes, making it one of the most comprehensive in the world.

The dictionary was conceived in the 1950s with the inadequacy of the existing Slavic etymological dictionaries in mind.^[1] Since 1961 the preparations began for the dictionary under the direction of Oleg Trubachev at the Russian Language Institute of the Russian Academy of Sciences in the USSR.^[2] In 1963 a trial edition of the dictionary was published.^[3] Since its inception, the dictionary has been published by the Department of Etymology and Onomastics of the Russian Language Institute.

The Editor-In-Chief in the period 1974—2002 was Oleg Trubachev. Trubachev passed away in 2002, at which point the role was taken up by Anatoly Zhuravlyov [ru]. Zhuravlev was the editor until vol. 40 (2016), which was co-edited by him and Zhanna Varbot [ru], who has continued editing the following volumes.

For every Proto-Slavic reconstruction an etymology is given, as well as the history of etymological research. Reflexes in all Slavic languages are listed, and so are the cognates in other Indo-European languages. Proto-Slavic accent and accentual paradigm is not reconstructed. Elements of Proto-Slavic morphology (affixes, desinences) are also not reconstructed. Over 2100 journals and books have been used while writing the published volumes of the dictionary.^[4] The complete dictionary is estimated to contain around 20 000 words.^[5]