C-3 was a C-class submarine of the Spanish Republican Navy. C-3 was built by Sociedad Española de Construcción Naval (SECN) in Cartagena, Spain, launched 20 February 1929, and commissioned on the 4 May 1929. She took part in the Spanish Civil War on the government side before being sunk by the German submarine U-34 on 12 December 1936.