Ernst Octavianus Moltzer (May 1, 1910 in Amsterdam – November 15, 1941 in the North Sea) was a sailor from the Netherlands, who represented his native country as at the 1936 Summer Olympics in Kiel.
Ernst, as crew member on the Dutch 6 Metre De Ruyter, took the 8th place with helmsman Joop Carp and fellow crew members: Ansco Dokkum, Kees Jonker and Herman Looman.