For the Italian language, you can use the Accademia della Crusca. It is the most prestigious linguistic institution in Italy and its role is to study and research the Italian language, changes in the language and understanding its transformations. In addition, this dictionary seeks to understand the reasons and influences that make a language a living organism in constant evolution and growth.
Follow the link for the dictionary:
This organization has been running for more than 400 years and is currently part of the European Federation of National Linguistic Institutions that adheres to the same criteria of safeguarding and analysing the various European languages.
Talking about Italian monolingual dictionaries, this article would not be complete without mentioning the Treccani Institute dictionary. Its purpose is to compile, update and publish the Italian Encyclopaedia of Sciences, Literature and Arts started by Jovanni Treccani and the works derived from these publications. This Institute is also recognized as a private entity of national interest and as a cultural institution independent of the Italian State and other bodies. Given its cultural importance, the President of the Republic is in charge of appointing the president.
Follow the link for the dictionary of this institution: