Framed by a wide range of factors, doctoral education has undergone a deep transformation, especially in the last two decades. The aim of this systematic literature review was to ascertain the dimensions in which the transformation of doctoral education has been revealed. The ultimate purpose was to understand how this transformation is related to and reflects the idea or concept of doctoral education, i.e., what this is or should be. The systematic review process involved the collection, systematisation and analysis of scientific texts on doctoral education to achieve a comprehensive picture. The analysis suggests the multidimensionality of the transformation in doctoral education, evidenced in aspects related to its foundations, objectives, methods, expertise, organisation and process. This seems, in turn, to indicate the coexistence of different ideas or concepts of doctoral education.