Trails are important elements in the natural and cultural landscape, and many ancient pathways have developed into routes of great significance for recreation and tourism in contemporary societies. By conducting a systematic quantitative literature review, this paper report on the status of international trail research and analyzes some of the key content with focus on trails for tourism and outdoor recreation in non-urban settings. For this purpose, we reviewed 195 research papers published in peer-reviewed academic journals. Results show that research on trails for tourism and outdoor recreation is primarily from English-speaking Western countries. The most studied trail-based activity is hiking, but there has been an increase in the number of studies researching multiple activities. Results also show that international trail research to a large extent is based on the natural sciences, and focus on environmental and managerial aspects of trail use. This review identifies gaps in trail research, especially in a socio-cultural context on topics such as heritage and public health. Research on conflicts between different recreational trail-based activities is also relatively scarce, as well as studies concerning conflicts between trail-based recreation interests and other land-use interests. We also identify a need for an exploration of the trail concept, as research has not yet articulated a clear definition of what a trail is. The paper also includes analyses of changes in trail-related research over time.