Asthma is a common chronic respiratory disease affecting people of all ages globally. The airway hosts diverse microbial communities increasingly recognized as influential in the development and disease course of asthma. Here, we review recent findings on the airway microbiome in asthma. As relationships between the airway microbiome and respiratory health take root early in life, we first provide an overview of the early-life airway microbiome and asthma development, where multiple cohort studies have identified bacterial genera in the infant airway associated with risk of future wheeze and asthma. We then address current understandings of interactions between environmental factors, the airway microbiome, and asthma, including the effects of rural/urban environments, pet ownership, smoking, viral illness, and antibiotics. Next, we delve into what has been observed about the airway microbiome and asthma phenotypes and endotypes, as airway microbiota have been associated with asthma control, severity, obesity-related asthma, and treatment effects as well as with type 2 high, type 2 low, and more newly described multi-omic asthma endotypes. We then discuss emerging approaches to shape the microbiome for asthma therapy and conclude the Review with perspectives on future research directions.