The Balkan sprachbund or Balkan language area is an ensemble of areal features—similarities in grammar, syntax, vocabulary and phonology—among the languages of the Balkans. Several features are found across these languages though not all apply to every single language. The Balkan sprachbund is a prominent example of the sprachbund concept.

The languages of the Balkan sprachbund share their similarities despite belonging to various separate language family (genetic) branches. The Slavic, Hellenic, Romance and Albanian branches all belong to the large Indo-European family, and the Turkish language is non-Indo-European.

Some of the languages use these features for their standard language (i.e. those whose homeland lies almost entirely within the region) whilst other populations to whom the land is not a cultural pivot (as they have wider communities outside of it) may still adopt the features for their local register.

While some of these languages may share little vocabulary, their grammars have very extensive similarities; for example:

The reason for these similarities is not a settled question among experts. Genetic commonalities, language contact, and the geopolitical history of the region all seem to be relevant factors, but many disagree over the specifics and degree of these factors.

The earliest scholar to notice the similarities between Balkan languages belonging to different families was the Slovenian scholar Jernej Kopitar in 1829. August Schleicher (1850) more explicitly developed the concept of areal relationships as opposed to genetic ones, and Franz Miklosich (1861) studied the relationships of Balkan Slavic and Romance more extensively.

Nikolai Trubetzkoy (1923), Kristian Sandfeld-Jensen (1926), and Gustav Weigand (1925, 1928) developed the theory in the 1920s and 1930s.

In the 1930s, the Romanian linguist Alexandru Graur criticized the notion of “Balkan linguistics,” saying that one can talk about “relationships of borrowings, of influences, but not about Balkan linguistics”.