Moholy-Nagy was born "László Weisz" in Bácsborsód, Hungary to a Jewish family. His cousin was the conductor Sir Georg Solti. He attended Gymnasium in the city of Szeged. He changed his German-Jewish surname to the Magyar surname of his mother's Christian lawyer friend Nagy, who supported the family and helped raise László and his brothers when their Jewish father, Lipót Weisz left the family. Later, he added “Moholy” to his surname, after the name of the town of Mohol (today in Serbia) in which he grew up. One part of his boyhood was spent in the family home near Mohol.
In 1918, he formally converted to the Hungarian Reformed Church; his godfather was his Roman Catholic university friend, the art critic Iván Hevesy. Immediately before and during World War I he studied law in Budapest and served in the war, where he sustained a serious injury. In Budapest, on leave and during convalescence, Moholy-Nagy became involved first with the journal Jelenkor (“The Present Age”), edited by Hevesy, and then with the “Activist” circle around Lajos Kassák’s journal Ma (“Today”). After his discharge from the Austro-Hungarian army in October 1918, he attended the private art school of the Hungarian Fauve artist Róbert Berény. He was a supporter of the Hungarian Soviet Republic, declared early in 1919, though he assumed no official role in it. After the defeat of the Communist regime in August, he withdrew to Szeged. An exhibition of his work was held there, before he left for Vienna around November 1919. He left for Berlin early in 1920.