Efthymios Nicolaidis was born in Athens. He obtained the Baccalauréat in France, and studied Physics at Paris XI-Orsay and History of Science at the Ecole des Hautes Etudes en Sciences Sociale, Paris (with R. Taton). Collaborator of the National Observatory of Athens (1979-1984), he joined the Programme of history of science of the Institute for Neohellenic Research of the National Hellenic Research Foundation in 1984. From 2003 he is the director of this programme. President (2013 - 2017) and Secretary General (2005-2009 and 2009-2013) of the International Union of the History and Philosophy of Science and Technology / Division of History of Science and Technology and member of the Council of the International Academy of History of Science. Coeditor of Almagest and of the Newsletter for the History of Science in Southeastern Europe. Coordinator of the programmes Hephaestus (E.U., FP7, Capacities), NARSES (E.U., National Strategic Reference Framework NSRF) and DACALBO (E.U., National Strategic Reference Framework NSRF).