This review article opens discussion on theories in futures studies by analyzing survey results from Finland Futures Research Centre and using the results as an entry point to discussing theoretical lineages found in the literature. The survey, conducted in 2019, included twenty-four responses from researchers and postgraduate students. Altogether 192 different theories or theoretical frameworks were identified. Social science theories and conceptual frameworks were particularly prevalent in the responses, and the most common recurring themes included systems, complexity, and anticipation. The responses are discussed in terms of three levels: philosophy of science, theories of futures studies, and theories in futures studies. Theories in futures studies are further divided into theories of action, practices, and behavior; theories of change; and theories on the micro-, meso-, and macro levels. The results are contextualized and complemented by proposing five functionally differentiated theoretical approaches: (1) theories for forecasting, (2) theories for representing futures, (3) theories for pursuing desired futures, (4) theories for making sense of anticipatory processes, and (5) radical epistemological critiques. The analysis is intended to open discussion on theories rather than provide an exhaustive list of the most important theories. Nevertheless, we can conclude that the field has a rich theory base which could be emphasized in futures education and developed further. It is crucial that actors in the futures field are aware of the theories that guide them because influential theories take part in making the future.