Mouni Sadhu was the pen name of Mieczyslaw Demetriusz Sudowski, a Polish-born author of spiritual, mystical, and esoteric subjects. He lived in Poland until World War II and eventually settled in Australia. He primarily wrote about Western and Eastern spirituality, as well as occultism, Hermeticism, and the Yoga traditions of India. His greatest personal influence was Ramana Maharshi. The name "Mouni Sadhu" means "silent monk" in Sanskrit.
His literary estate was left to the Australian Society of Authors, of which he was a member.