The terms 'authenticity' and 'authentic' have been used increasingly frequently in educational contexts over the past decades. In science education, authenticity is claimed to be a crucial concept, inter alia, for students' motivation and interest in science. However, both terms are used, defined and conceptualised in various and ambiguous ways. So far, however, a model to integrate and structure the various conceptualisations, definitions and findings with their implementation in a teaching context is lacking. In this contribution, we introduce such a model, coherently integrating a broad range of work done by previous authors. Meanwhile, the model is flexible enough for future extensions and refinements. As many authors have shown, the concept of authenticity is multidimensional. In the present contribution, we therefore introduce a multidimensional model, explaining each dimension with reference to previous work on authenticity before integrating them as the complete model. We will outline a tool for practitioners and researchers which is based on the introduced model.