This thesis offers a Marxist humanist political economic analysis of radical media. Radical media has been under-researched and underappreciated as a subject. Modern theorists have positioned it either as a fringe subject or as a diffuse topic without definitional clarity used interchangeably with concepts such as alternative and independent to describe non-mainstream media, communications and digital society. This thesis aims to clarify the conceptualisation of radical media and consider the concrete publications and platforms, shaped by radical media actors, that have developed in the digital age. This analysis is grounded by an understanding of the historic development of theories of and practices of radical media. A multi-methods research design is used as a basis for three analyses of three radical media samples: a typology analysis of concepts of radical media in the digital age (1995–2019), a content analysis of radical media publications and platforms in the UK, USA and Ireland (2016–2019) and thematic analysis of semi-structured interviews with radical media actors in the UK, USA and Ireland (2016–2019). Radical media is re-defined and a typology containing radical critical, community, activist and institutional media is proposed. Shifts in radical media production are explored and the emergence of semi-professionalised, intellectual publications and platforms, interlinked politically to the revival of Marxism and Social Democracy is noted. These radical media publications and platforms from above are in tension with a ‘periphery’ with emphasis on reporting from everyday experiences and struggles, from below and outside the state. These are significant advances in our understanding of radical media as part of the field of critical communication and politics within digital society.