Ludwig Derleth (3 November 1870 – 13 January 1948) was a German writer.
He was born in Gerolzhofen in Bavaria. After studying philosophy and literature Derleth worked as a college level teacher of ancient languages. While living in Munich he became part of the Stefan George entourage and also the Munich Cosmic Circle of Alfred Schuler and Ludwig Klages, which broke up in 1904.
He published his first poems in George's Blättern für die Kunst and in the Jugend magazine Pan. In 1904 he published his "Proclamations" for a reformed and reorganized Catholicism. Derleth spent 40 years completing his major work Der fränkische Koran. He may have served as a model for Thomas Mann's 1904 novel At the Prophet's.
Other works: Seraphinische Hochzeit (1939) and Der Tod des Thanatos (1945).