Japanese submarine I-56

IJN I-56 has been the name of two Japanese submarines, and may refer to:


 * Japanese submarine I-156, a Kaidai-class cruiser submarine commissioned in 1929 and scuttled in 1946 before she was renumbered on 20 May 1942
 * Japanese submarine I-56, a B3-class cruiser submarine commissioned in 1944 and lost in 1945