Enciclopedia Italiana di Scienze, Lettere ed Arti – Idea, Esecuzione, Compimento (1939) is a commemorative volume summarizing the conceptual foundations, editorial methodology, and realization of the Treccani Encyclopedia project. Published at the completion of the main encyclopedia series, it documents the cultural, institutional, and academic efforts behind its creation. The volume outlines editorial strategies, contributors’ roles, and ideological influences within the context of early 20th-century Italian scholarship. It is a key historical source on national encyclopedic production and intellectual organization during the interwar period.