Protists are the most diverse eukaryotes. These microbes are keystone organisms of soil ecosystems and<br/>regulate essential processes of soil fertility such as nutrient cycling and plant growth. Despite this,<br/>protists have received little scientific attention, especially compared to bacteria, fungi and nematodes in<br/>soil studies. Recent methodological advances, particularly in molecular biology techniques, have made<br/>the study of soil protists more accessible, and have created a resurgence of interest in soil protistology.<br/>This ongoing revolution now enables comprehensive investigations of the structure and functioning of<br/>soil protist communities, paving the way to a new era in soil biology. Instead of providing an exhaustive<br/>review, we provide a synthesis of research gaps that should be prioritized in future studies of soil<br/>protistology to guide this rapidly developing research area. Based on a synthesis of expert opinion we<br/>propose 30 key questions covering a broad range of topics including evolution, phylogenetics, functional<br/>ecology, macroecology, paleoecology, and methodologies. These questions highlight a diversity of topics<br/>that will establish soil protistology as a hub discipline connecting different fundamental and applied<br/>fields such as ecology, biogeography, evolution, plant-microbe interactions, agronomy, and conservation<br/>biology. We are convinced that soil protistology has the potential to be one of the most exciting frontiers<br/>in biology.