Oleg Valerianovich Basilashvili was born on 26 September 1934 in Moscow, Russian SFSR, Soviet Union. His father, named Valerian Basilashvili, was a director of the Moscow Polytechnical College. His mother, named Irina Ilyinskaya, was a teacher of linguistics.

In 1956 Oleg Basilashvili graduated from the Acting School of the Moscow Art Theatre (MkHAT), where he had studied under Pavel Massalsky. His group was one of the most talented: among his group mates there was Yevgeniy Yevstigneyev, Mikhail Kozakov and Tatiana Doronina, his first wife. He made his film debut as a young groom in film Nevesta (aka The Bride, 1956) by director Grigori Nikulin based on a story by Anton Chekhov. At that time together with his first wife, Tatiana Doronina, Basilashvili joined the troupe at the Bolshoi Drama Theatre (BDT) in Leningrad under the leadership of the legendary director Georgi Tovstonogov. Since 1959 Basilashvili has been a permanent member of the troupe at the BDT in St. Petersburg. There his stage partners were such stars as Kirill Lavrov, Tatyana Doronina, Alisa Freindlich, Lyudmila Makarova, Svetlana Kryuchkova, Zinaida Sharko, Valentina Kovel, Innokenti Smoktunovsky, Oleg Borisov, Pavel Luspekayev, Sergei Yursky, and many other remarkable Russian actors. Basilashvili’s most memorable stage works were in the play Uncle Vanya by Anton Chekhov, Kholstomer based on the eponymous story of Leo Tolstoy, The Lower Depths by Maxim Gorky, and other classic plays directed by Georgi Tovstonogov at the BDT in St. Petersburg.

During the 1990s he was a visible political figure in Russia, and was elected the representative of Leningrad (St. Petersburg) in 1990. Eventually he became a member of the pro-democratic group of representatives in the Russian Parliament, and a supporter of such politicians as Anatoly Sobchak and the first Russian President Boris Yeltsin. Oleg Basilashvili was a strong proponent of returning the original name to the city of St. Petersburg. He quit politics after 2000, and focused on his acting career.

In 2001 Oleg Basilashvili starred in Karen Shakhnazarov’s comedy Yady, ili vsemirnaya istoriya otravleniy (Poisons or the World History of Poisoning) (2001). The actor performed both as pensioner Prohorov and the Pope Alexander VI Borgia in it.