This chapter addresses the relationship between urban planning and social justice. Since the primary way in which urban planning affects social justice is through spatial arrangements, spatial justice constitutes the focus of the discussion. Making justice a primary goal for urban policy rests on both moral and practical arguments. Within the scholarly literature a critique of urban planning as unjust, rooted in Marxist political economy, began in the 1970s. Reforms that promote justice can be achieved within democratic capitalist political economies when popular movements back progressive leadership. Within the left the possibility of achieving greater equity within global capitalism has been subject to disagreement since the nineteenth century. The chapter begins by addressing the question of why justice should be given priority, examines the role of planners in effecting or blocking its application, looks at the history of value emphases in planning, considers current debates, and concludes by discussing what can be done.