D78 may refer to:
D. 78, Aria "Son fra l’onde" for soprano and piano, composed by Franz Schubert in 1813 , Long Island-class escort carrier built by the US in 1939–1940, operated by the Royal Navy during World War II , Admiralty V class destroyer of the Royal Navy , Admiralty modified W class destroyer built for the Royal Navy London Underground D78 Stock, type of sub-surface rolling stock which operated on the District line of the London Underground