This book introduces the concept of activist music research, emphasising action and social responsibility and suggests that music research can be used to promote social and ecological justice. This is discussed in a series of position papers by music researchers who engage in public debate in their various roles - educator, critic, journalist, DJ, producer, promoter - and work with other actors in civil society and culture. The book suggests that we are experiencing an activist turn in music research, evidenced by the growing number of projects and publications discussing inequalities in musical practices and the impact music research can have on these inequalities. This idea is explored in a series of position papers and contemplative texts, where music researchers, music educators, and artistic researchers reflect on how their work and the position they occupy as professionals in society serves eco-social justice and equity. What is the point of studying and teaching music in an age of ecocide, neo(liberal)-colonialism, rampant racial inequities, persistent gender identity and sexual orientation discrimination? What does social and ecological responsibility and sustainability mean in music research?