Yeru or Eru (Ы ы; italics: Ы ы), usually called Y [ɨ] in modern Russian or Yery or Ery historically and in modern Church Slavonic, is a letter in the Cyrillic script. It represents the close central unrounded vowel /ɨ/ (more rear or upper than i) after non-palatalised (hard) consonants in the Belarusian and Russian alphabets, and after any consonant in most of Rusyn standards, where it represents the unrounded close-mid back unrounded vowel sound.

The letter is usually romanised into English and most other West European languages as ⟨y⟩: Krylov (family name, Крылов). That spelling matches Polish, which uses ⟨y⟩ to represent a very similar sound. Russian ⟨ы⟩ is used to transliterate Polish ⟨y⟩ into Cyrillic: Maryla (Марыля). However, Latin ⟨y⟩ may be used for other purposes as well (such as for ⟨й⟩, or as part of digraphs, e.g. ⟨я⟩).

In most Turkic languages that use Cyrillic, ⟨ы⟩ represents the close back unrounded vowel /ɯ/, like in Kazakh, Kyrgyz, etc.