This chapter lays the theoretical groundwork for understanding how youth in The Hague engage with Sustainable Development Goal 16 (Peace, Justice, and Strong Institutions). Positioned as the International City of Peace and Justice, The Hague provides a distinct lens through which to examine young people’s interpretations of justice, safety, and institutional trust. Drawing from a diverse range of theories—including social cohesion, social identity theory, intersectionality, critical pedagogy, and sustainability—the chapter constructs a multidimensional framework for analysing youth engagement within a city marked by socioeconomic and cultural divides. Participatory action research is explored both as a methodology and as an ethos for amplifying youth voices. The chapter raises critical questions about how youth connect global sustainability issues with local justice concerns, especially in contexts shaped by inequality and marginalisation. This theoretical foundation supports the empirical inquiry that follows and argues for youth participation as central to shaping inclusive, just, and sustainable urban futures.