Vincas Mickevičius (Polish spelling: Mickiewicz), known under his pen name Kapsukas (7 April [O.S. 23 March] 1880 – 17 February 1935), was a Lithuanian communist political activist, publicist and revolutionary.

As an active member of the Lithuanian National Revival, he wrote for and edited many Lithuanian publications and joined the Lithuanian Social Democratic Party. As his views turned from socialism to communism, he became one of the founders and leaders of the Lithuanian Communist Party and headed the short-lived Lithuanian Soviet Socialist Republic and Lithuanian–Belorussian Soviet Socialist Republic (Litbel) in 1918–1919. After the fall of these republics, Mickevičius left for Soviet Russia, where he continued to lead the Lithuanian communists and worked for the Communist International (Comintern).