Grypsera (from Low German greips meaning mind) is a distinct non-standard dialect of the Polish language, used traditionally by recidivist prison inmates. It evolved in 19th century in the areas of the Russian partition.

The basic substrate of the dialect is Polish, but with many notable influences (mostly lexical) from other languages used in Polish lands at that time, most notably Yiddish, German, Ukrainian and Russian. It was also heavily influenced by various regional dialects of Polish language, most notably the bałach of Lwów and the Warsaw dialect.

Initially it served the role of a secret language , but in late 19th century it became a standard ethnolect of criminals. The Grypsera is constantly evolving to maintain the status of a language understood only by a selected group of inmates and not by the wards or informers. Because of that it is currently one of the most rich lexically dialects of the Polish language. Also, it is not possible to prepare a comprehensive dictionary of that dialect since it differs from prison to prison.

Phonetically, the Grypsera is similar to the Warsaw dialect and shares its most notable features of assimilation of i into y (IPA [] into [i]) and disappearance of nasal vowels, especially in word-final syllables.