The Leonardopoulos–Gargalidis coup attempt (Greek: Κίνημα Λεοναρδόπουλου-Γαργαλίδη) was a failed military coup launched on 22 October 1923 in the Kingdom of Greece by pro-royalist military officers under the Lieutenant Generals Georgios Leonardopoulos and Panagiotis Gargalidis, and the Colonel Georgios Ziras. Its failure discredited the monarchy and contributed decisively to the establishment of the Second Hellenic Republic in March 1924.