Recent social psychological perspectives on the legitimation of discriminatory attitudes and behaviors toward formerly colonized groups have emphasized the role of postcolonial ideologies in perpetuating social asymmetries and resistance to social inclusion measures social (Sibley et al., 2008; 2016; 2018; Newton et al., 2018). In particular, the literature has shown that the content of colonial beliefs in various postcolonial societies organize contemporary negative attitudes toward colonized groups and resistance to public policies that promote inclusion and access to material resources for people from colonized (and typically socially disadvantaged) groups (Castro et al., 2022; Valentim & Heleno, 2018; Satherley & Sibley, 2018). However, because the content of colonial beliefs is primarily derived from the socio-historical narrative of each society, the structure and function of these postcolonial ideologies in key dimensions of asymmetrical relations between groups continues has still to be fully elucidated. This is important because by examining the psychosocial substrate of colonial ideological thinking we can elucidate relationships that have remained unanswered. The LUSO project, therefore, proposes to examine the structure of postcolonial ideological thinking and the function it plays in contemporary social inequalities. It assumes that it can be conceptualized as a style of colonial thinking that emerged from social concepts, politically institutionalized to justify geopolitical strategy and shape collective representations about the colonial past (Castro et al., 2022; da Silva & Cabral, 2020; Licata et al., 2018; Sibley & Osborne, 2016; Valentim, 2011). Previously theorizing developed by members of LUSO, identifies at least four organizing components of postcolonial ideological thinking that integrate historical denial of injustice (Pereira et al., 2018; Sibley & Osborne, 2016), scope of justice (Lima-Nunes et al., 2013; Opotow, 1996), miscegenation (Cabecinhas & Feijó, 2010; Valentim, 2011), and development (Licata et al., 2010; 2018). These four components illuminate the psychosocial process of the emergence, structuring, and political implementation of colonial ideological thinking, which in the past served to legitimize the maintenance of colonial empires and today legitimizes the existence of social asymmetries between socially advantaged (i.e., formerly colonizers) and disadvantaged groups (i.e., formerly colonized). This clarification of the organizing components of postcolonial ideologies will allow us to answer the questions that remain unanswered, namely: To what extent are these ideologies socially accepted today by representing a legitimating mechanism in the relationship between a general orientation toward dominance and prejudice and hostility toward formerly colonized groups? To what extent does adherence to postcolonial ideologies vary across a) generations and b) group social status? The general objective of LUSO is to analyze how the organizing dimensions of colonial ideological thinking persist and operate in Portuguese society, and what function they have in legitimizing discriminatory attitudes and behaviors toward formerly colonized groups. The research questions will be addressed in four working packages (WP). Specifically, LUSO will (1) develop and validate a new instrument measuring the organizing dimensions of Luso-tropicalism, as a postcolonial ideological thinking, which we propose to be organized in four latent factors (WP1); (2) test the social normativity of Luso-tropicalism (WP2); (3) test if it operates as a legitimizing myth within the general framework of intergroup ideologies (WP3), by proposing that it can dampen support to inclusive social policies (i.e., a suppression effect) and facilitate discriminatory attitudes and behaviors toward disadvantaged people from formerly colonized groups (i.e., a foster process); (4) examine the social diffusion of these assumptions with a sample of the Portuguese population (WP4), while testing potential moderators of those relationships, namely socialization patterns (i.e., intergenerational differences) and group status (high SES vs low SES). LUSO will conduct a multi-method research program that includes qualitative and quantitative studies, correlational and experimental research designs, and an online survey. LUSO will make a substantial contribution to the study of the psychosocial processes of colonial legacy in the national context and will significantly advance the knowledge about the structure of postcolonial ideological thinking in the international scene.