Xifias (, "swordfish") was a Greek submarine (actually called a "submersible", καταδυόμενον, according to the then current French terminology) which served during World War I. It was the third submarine to enter service in the Greek navy, and the second and last vessel of the Delfin class. It was taken over by the French in 1916, and decommissioned in 1920 without seeing action.