Sergei Mamaev

An activist from Yoshkar‑Ola, a city east of Moscow in central Russia. On 22 July 2025, he reported that he had been detained in a case concerning an "extremist organisation" linked to the activities of Alexei Navalny’s regional offices. The following day, he was remanded in custody. The prosecution appears to have been based on social media posts and participation in events dedicated to Navalny. On 16 February 2026, Mamaev was sentenced to two years and eight months in a general-regime penal colony.