The ruling United Russia party is expected to win after a sweeping crackdown that crushed Kremlin critic Alexei Navalny's movement and barred opponents from the ballot.
The expected win by United Russia party will be used by the Kremlin as proof of support for President Vladimir Putin despite malaise over years of faltering living standards.
The party that backs Russia's 68-year-old leader faces a ratings slump, state pollsters say, but remains more popular than its closest rivals on the ballot, the Communist Party and nationalist LDPR party, which often back the Kremlin.
United Russia holds nearly three quarters of the State Duma's 450 seats. That dominance last year helped the Kremlin pass constitutional reforms that allow Putin to run for two more terms as president after 2024, potentially staying in power until 2036.