Cyanobacteria are ancient, globally widespread photosynthetic prokaryotes that synthesize potent toxins and form blooms, a major ecological and human health problem worldwide. Conditions promoting massive bloom proliferation have been extensively studied, but mechanisms causing their abrupt termination are poorly understood. Cell death plays a vital role in the dynamics of ephemeral blooms, determining the flow and fate of organic matter and nutrients. In recent decades, regulated cell death (RCD) induced by biotic or abiotic stresses has become a major mechanism to explain the disappearance of blooms of harmful algal species. However, the molecular basis and physiological mechanisms behind RCD in cyanobacteria are still largely unknown. This chapter aims to describe recent advances in regulated cell death, its nomenclature, implications for cyanobacterial fitness, and ecological relevance. Additionally, we describe methods to study cell demise in this group of photosynthetic organisms. This information contributes to increasing our understanding of how cyanobacteria cope with environmental stress and activate RCD and opens new applications in biotechnology, for instance, the development of new technologies to control harmful blooms and ensuring water quality, and preserve the health of the population.