Across the tree of life organisms have evolved in environments with a predictable rhythm of light and dark. Master clocks in the individual integrate daily light cues to organize genetic, physiological, and behavioral outputs. Artificial light at night disrupts those patterns and has far-reaching consequences for species of all chronotypes. Though most abundant in urban environments, the effects of light pollution are far-reaching into rural and remote natural areas. Furthermore, the intensity, spectral composition, and source of light pollution can lead to species-specific responses, complicating effects at the level of ecosystems. A brief introduction will overview the wide range of consequences of artificial light at night and introduce the major themes of our invited speakers. This symposium showcases an eclectic selection of comparative research from varied fields of study including development, physiology, population biology, and ecology. We aim to identify common mechanisms, challenges, and avenues for future research by bringing together speakers and attendees with diverse and complementary research programs.