D61 may refer to :HMAS Swan (D61), a 1915 Royal Australian Navy River class torpedo boat destroyer HMS Calypso (D61), a 1917 British Royal Navy C class cruiser HMS Ilex (D61), a 1937 British Royal Navy I-class destroyer INS Delhi (D61), a 1995 Indian Navy Delhi class destroyer JNR Class D61, a Japanese steam locomotive converted from the JNR Class D51 D61 motorway (Slovakia) SPS Churruca (D61), a 1972 Spanish Navy Gearing-class destroyer Queen's Gambit Declined, Encyclopaedia of Chess Openings code