Approaching Alain Badiou as a militant thinker committed to diagnosing political disorders of his time and waging theoretical battles to advance the communist hypothesis, this book focuses on the principal ambiguity of Badiou’s project, which concerns the enigmatic relationship between philosophy and politics. On the one hand, his mature texts maintain a strict line of separation between the two disciplines. On the other hand, Badiou consistently links the philosophical pursuit of true life to a political revolt against injustice and inequality. Rather than treating Badiou as a builder of grand ontological systems, this book approaches the French philosopher as a combative polemicist and thinker of the contemporary moment. Not only does it take into account the development of Badiou’s thinking from Sartre, Althusser, and Lacan as well as the yet unexplored relationship between Badiou’s thinking and that of Foucault, but beyond that, places him in dialogue with contemporary thinkers such as Nancy Fraser and Wendy Brown. The Philosopher Militant not only diagnoses the political malady of the epoch, but also proposes a course of treatment and actively intervenes in the current situation. Seeking to foreground the actuality of Badiou’s work, Gordienko provides commentary on the philosopher’s canonical texts, exploring the relevance of his ideas to the latest political developments such as the election of Trump, as well as ‘the dream of the lockdown’ during the COVID-19 pandemic. As such, this book aspires to thinking with Badiou.