Through an exploratory bibliographic-documentary research, this dissertation seeks to analyze the Library Advocacy and how this movement has manifested itself in several countries. For this purpose, a literature review was carried out on the subject, considering concepts such as democracy and politics, the field of public policies, besides the meaning of the term advocacy and the concept attributed to it. As a fundamental point for a better understanding of the Library Advocacy, it was sought to identify the origin, function, role and importance of Public Libraries in today's society, so that it was possible to study how and why this movement emerged, was structured and is spreading throughout the world. Based on a review of relevant literature, it has been identified that the International Federation of Library Associations and Institutions (IFLA) and the Bill & Melinda Gates Foundation (BMGF) have been developing programs at the global level to strengthen libraries which, in addition to providing training for librarians, also finance initiatives related to the Library Advocacy. Five global programs were identified, four from IFLA and one from the BMGF. They are: The Library Development Program (LDP), the Building Strong Library Associations Program (BSLA), and the International Advocacy Program (IAP) of IFLA and the Global Libraries (GL) of the BMGF. As a result of the review, it was possible to consolidate a classification matrix of types of advocacy initiatives that could be developed by libraries: (a) structuring initiatives: Related to the strengthening of the librarian sector in the country or the national librarian association; (b) Training initiatives: Focused on vocational training for advocacy / leadership development / policy action; (c) Awareness-raising initiatives: Initiatives aimed at sensitizing the population to the value of libraries; and (d) Political initiatives: Actions and strategies that highlight the search for dialogue with the government on the positioning of libraries in public agendas. From this point, a mapping and categorization of the advocacy initiatives that have been conducted by national or regional associations of libraries around the world have followed, in order to understand how this movement has spread and structured in the librarian communities. Through the consult of the national library association websites and the reports of the global programs, 80 initiatives were identified that received funding from the global programs, as well as 97 other initiatives undertaken / initiated between 2010 and 2018 and proposed / conducted within the scope proposed here. Thus, 177 initiatives were identified in at least 125 countries, of which only 159 could be classified as follows: 19 structuring initiatives, 96 training initiatives, 21 awareness-raising initiatives and 23 political initiatives. According to this sampling, 82.4% of the initiatives occurred in less developed countries. It can be seen, therefore, that in these countries, advocacy projects have been in progress for some...