Since the very first steps of space exploration, fungi have been recorded as contaminants, hitchhikers, or as part of missions’ crews and payloads. Because fungi can cause human disease and are highly active decomposers, their presence in a space-linked context has been a source of major concern given their possible detrimental effects on crews and space structures. However, fungi can also be beneficial and be used for many space applications. The exact effects on fungi are not always clear as they possess high adaptability and plasticity, and their phenotypes and genotypes can undergo several changes under the extreme conditions found in space, thus leading to different results than those we would have on Earth. Understanding and analysing these aspects is the subject of astromycology, a research field within astrobiology. The impending situation of a resurgent space race is expected to boost astromycology’s visibility and importance. However, researchers lack both a framework and a solid base of knowledge from which to contextualise their work. This critical review addresses this gap by conceptualising the field of astromycology, covering key research and current questions pertaining to the field, and providing a relevant research instrument for future work.