Oscar Lvovich Ryvkin (Russian: Оскар Львович Рывкин; 4 January 1899 – 7 August 1937) also known by his alias O. Skar[1] was a Soviet politician that served in various positions including First Secretary of the Central Committee of the Komsomol, First Secretary of the Krasnodar City Committee of the Communist Party of the Soviet Union, and a member of the Central Control Commission.

After the February Revolution, he joined the Red Guards as a fighter and served as the Secretary of the Petrograd Socialist Union of Workers' Youth.

[4] On June 19, 1917, Ryvkin published an article in Pravda under his pseudonym O. Skar called "An Open Letter to Comrades, Workers, and Soldiers."

In the article, Ryvkin called for the cancelling of the Provisional Government's resolution that only allowed citizens older than twenty-one years old to vote.

After graduating from the Institute of Red Professors in 1934, Ryvkin served as the First Secretary of the Krasnodar City Committee of the Communist Party of the Soviet Union.