Guillermo Néstor Mastrini (born January 24, 1967) is an Argentine researcher and professor specializing in mass media policy and the right to information. He holds a degree in Communication Sciences from the University of Buenos Aires. He was one of the first three graduates of the program, served as academic secretary, and was its director from 2006 to 2008. He holds a PhD in Information Sciences from the Complutense University of Madrid. He is one of the leading figures in the field in Argentina and a driving force behind the Audiovisual Communication Services Law, approved by Congress on October 10, 2009.

He is a professor at the National University of Quilmes, where he also directed the Master's Program in Cultural Industries. He is also a tenured professor of Communication Policy and Planning at the Faculty of Social Sciences (UBA) and a professor at the universities of Quilmes, Córdoba, and the National University of General San Martín (where he teaches the course "Industries of Culture and Communication" in the Specialization in Cultural Management and Cultural Policies). In 2017, he visited several communication faculties at Colombian universities, most notably UniMinuto, where he gave a series of lectures on the importance of communication policies in the region.