Lidia Semyonova (1925–2015) – Docent of the Chair of Material Engineering of the Riga Polytechnic Institute from 1968 to 1990. >>

Maria Semyonova (1910–1988) – Docent of the Faculty of Philology of the Latvian State University, Candidate of Philological Sciences. Specialist in the field of dialectology and comparative grammar of the Russian and Latvian languages. >>

Ulyana Semyonova (1952–2026) – as a member of the USSR basketball team twice won the Olympic gold medals (1976, 1980). The best Latvian basketball player of the 20th century. >>

Yakov Serafimov (1884–1949) – a teacher  of Math at the Riga city Russian gymnasium (former Lomonosov). >>

Julia Serafimova (née Baskakova; 1887–?) – a singer and vocal teacher, adocnt of the Latvian Conservatory. >>

Seraphim (secular name Semyon  Protopopov; 1818–1891) –  a bishop of Riga and Jelgava (1874-1877). >>

Lydia Seraya (1936–2020) –  a teacher of Latvian and Russian. >>

Tarasiy Seredinsky (1822–1897) – an archpriest.
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Nikolay Sergeyev (1876–1951) – a choreographer, teacher and ballet dancer, worked at the Latvian National opera as ballet producer in 1922–1925. >>

Varvara Sergeyeva (1902–1997) – a Full Member of the Latvian SSR Academy of Sciences, prominent expert in the chemistry of wood. >>