Seidozerite is a sorosilicate from the seidozerite supergroup (a "titanium disilicate"). It was first described by Semenov, Kazakova and Simonov in 1958. Its chemical formula is Na<sub>4</sub>MnZr<sub>2</sub>Ti(Si<sub>2</sub>O<sub>7</sub>)<sub>2</sub>O<sub>2</sub>F<sub>2</sub> and its type locality is 'Pegmatite No. 58', Lake Seydozero, Lovozero massif, Kola peninsula, Murmansk Oblast.