Johannes Lepsius was born in Potsdam, in Germany, in 1858. Become an evangelical pastor, following the first massacres in Turkey (three hundred thousand victims), in 1895 he set up the "Deutsche Orient-Mission", the aim of which was to run orphanages for Armenian children who had survived the massacres.
In 1896 he published "Armenians and Europe", his first documented report on the atrocities committed by the sultan Abdul Hamid II, an ally of Wilhelm II. In aid of the Armenian victims of persecution he set up the Lepsius Foundation, with various branches in Anatolia. From 1912 to 1914 he took part in diplomatic moves and conferences on the Armenian question in Constantinople, Paris, London and Bern.
At the beginning of the Armenian genocide of 1915 he had a dramatic interview with Enver Pasha, minister of War, during which he tried in vain to prevent the systematic deportation of the Armenian people.
In 1916 he had his "The Condition of the Armenian People in Turkey" printed privately, defying the Turkophile German censorship, which nevertheless managed to confiscate a number of copies.
Taking refuge in Holland, he kept up his struggle on behalf of the Armenians from there. He wrote the documentary volume entitled "Germany and Armenia 1914-1918" in which he exposed German complicity in the genocide of the Armenians. He testified at the trial against Soghomon Tehlirian, the assassin of Tal'aat Pasha, Turkish minister of the Interior. Thanks also to his testimony, Tehlirian was acquitted. In 1923 he started preparations for the foundation of an Armenian Academy in Potsdam.
He died in Merano, Italy, in 1926.