Otto Magnus Ludwig Gerhard Graf von Moltke von Rantzau (13 August 1851 – 13 January 1881), also known as Otto von Moltke, was a German-Danish military officer who fought in the Franco-Prussian War in 1870 and, after emigrating to Chile in 1876, in the War of the Pacific in 1879. He was killed in battle in 1881, during this last war.