This dissertation explores the construction of Filipino national identity by examining the Philippine national government's appropriation of Filipino Martial Arts (FMA) between 1975 and 2010. FMA's nationalization offers a window into the larger dynamics of nation-building in the Philippines. Having been colonized for nearly four centuries (1565-1946), the Philippine national government reified the Filipino nation by appropriating older symbols as national ones, and with the purpose of articulating a unique Filipino national identity. The nationalization of FMA is analyzed using Benedict Anderson's constructivist interpretation of nations as 'imagined communities'. The dissertation argues that in order to understand the logic behind the national government's nation-building project using FMA, Filipino postcolonial anxieties over national identity (or their perceived lack of) must be taken into consideration. In this regard, FMA's nationalization is engaged with Anthony Smith's concept of the ethnie (ethnic community). Studying the history of how decentralized indigenous martial arts practice became institutionalized in FMA clubs, the dissertation finds that FMA as an ethnographic concept was formulated mainly since the 1970s in consonance with its commercialization, increasing popularity and nationalization. By looking at how national identity is represented in FMA films and in reconstructions of the national hero Lapulapu, the dissertation argues that FMA practitioners seek to highlight their localized identities by inserting their own symbols and interpretations into the national identity being articulated. This process, termed the 'reverse appropriation' of nationalism, was a way for FMA clubs to preserve their local institutions and identities from being totally consumed by the nationalization and nation-building project.