https://www.epo.org/en/service-support/faq/searching-patents/asian-patent-information/russian-federation/filing-grant/what

What language must I use for patent applications in Russia?

The request for grant must be filed in Russian. Other documents pertaining to the application may be submitted in Russian or another language. If these other documents are submitted in another language, a translation into Russian must be attached to the application. If this translation is not provided, the applicant will be asked to file a translation into Russian within three months. The procedural language is Russian.

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