1 Agcaoili, Babaylan, Cojuangco, I thought all Filipinos had Spanish Last Names: The Administrative and Institutional Intent Behind the Catálogo Alfabético de Apellidos’ (Alphabetical Catalogue of Last Names) Implementation in Colonial Philippines Alfonso Ralph Mendoza Manalo Abstract The Catálogo Alfabético de Apellidos was issued as part of a royal decree in 1849 by Governor and Captain General Narciso Clavería, systemically implementing a surname naming system modelled after that of Spain across the Philippines. The Catálogo can be credited with the widespread use of Spanish surnames throughout the archipelago and its inhabitants today, with many of today's Filipino surnames being found within the Catalogue. This article argues that the Catálogo Alfabético de Apellidos was not decreed with the purpose of Hispanizing Filipino surnames but rather the Hispanization of Filipino surnames was a direct result of its implementation. This is done by highlighting excerpts from the decree itself that indicate the decree's policy intent and the gaps in its directives should it have been written with the intent of Hispanizing Filipinos (i.e. the omittance of Spanish naming patterns and allowing wealthy non- Spanish individuals to keep their Chinese and or Indigenous surnames). However, this paper seeks to demonstrate how the Catálogo was a direct reflection of the existing social, racial, and class hierarchies in the Philippines; acting as a means to institutionalize these differences through the assignment of surnames.