How to match Cyrillic characters with a regular expression

It depends on your regex flavor. If it supports Unicode character classes (like .NET, for instance), \p{L} matches a letter character (in any character set).

To match only Russian Cyrillic characters use:

[\u0401\u0451\u0410-\u044f]

which is the equivalent of:

[ЁёА-я]

where А is Cyrillic, not Latin. (Despite looking the same they have different codes)

\p{IsCyrillic}, \p{Cyrillic}, [\u0400-\u04FF] which others suggested will match all variants of Cyrillic, not only Russian

If your regex flavor supports Unicode blocks ([\p{IsCyrillic}]), you can match Cyrillic characters with:

[\p{IsCyrillic}] or [\p{Cyrillic}]

Otherwise try using:

[U+0400–U+04FF]

For PHP use:

[\x{0400}-\x{04FF}]

Explanation:

[\p{IsCyrillic}]

Match a character from the Unicode block "Cyrillic" (U+0400–U+04FF) «[\p{IsCyrillic}]»

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Note:

Unicode Characters list and Numeric HTML Entities of [U+0400–U+04FF] .