Rapidly increasing migration to urban areas in the 21st century has resulted in the rise of megacities. These megacities are defined by their dialectic conditions of massive economic, social, and political power and the marginalization and exploitation of these migrants and other oppressed communities. These communities are increasingly living in marginalized neighborhoods of megacities where they experience second-class citizenship - even for those who are granted de jure citizenship by the state. Although extensive research has explored citizenship education in marginalized communities in the United States and globally, there is a gap in exploring what citizenship education looks like in schools that have a social justice mission and educate marginalized communities within global megacities. This year-long ethnographic case study explores how IS 445, a Bronx public middle school, teaches justice-oriented critical citizenship for marginalized Black and Brown communities. The study included interviews with ten staff members and observations in two different social studies classrooms and of larger school policies and practices. The resulting data show that staff at IS 445 understand citizenship as connected to social action; education for citizenship therefore includes the core components of: 1) centering love and empathy, 2) promoting multiple perspectives and identities, and 3) empowering insurgency through creativity and entrepreneurship. These goals are supported by specific personal structures, rules, cultural norms, curricular and extracurricular structures, and teacher curricular and pedagogical choices. The combination of goals, structures, and teacher practices form a framework that I call "radical urban citizenship." Educators who teach and work in these communities and who aim to provide a justice-oriented civic education should consider ways to incorporate components of this radical urban citizenship framework into their classes and schools. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]