César Guillermo Castillo Reyes (Spanish pronunciation: [ɡiˈʝeɾmo kasˈtiʝo ˈreʝes]: born 17 March 1966) is a Guatemalan attorney and politician who served as the 17th vice president of Guatemala from 2020 to 2024.

He studied his primary education at the Salvador Osorio School, the secondary at La Salle College, and graduated as a Teacher at the Alejandro Córdova Mixed Normal Institute.

of International Technical Cooperation until January 2004, when he resigned to join Óscar Berger's cabinet after being appointed First Vice Minister of Labor and Social Welfare, a position he held until May 2005[4] when he was called to assume the position of General Manager of the INTECAP – Training Institute until April 2009, during these years he met and worked with Alejandro Giammattei who at that time was director of the Penitentiary System, as heads of their respective institutions they had to work together, who would later become the presidential formula.

[5] In 2009, he was elected by the Guatemalan Congress as magistrate of the Court of Appeals of the Contentious in the Judicial Branch and served as such until March 2014.

He participated in the union elections of the board of directors of the Bar Association and Notaries of Guatemala of the year 2009 as treasurer within the payroll and exercised in the period from 2009 to 2011.