This definition of professional nursing was developed at the Institute of Nursing Science, University of Basel, in collaboration with the group of experts from the project "Future of Swiss Medicine" of the Swiss Academy of Medical Sciences. Starting points were existing definitions and a list of desirable contents. Using Grounded Theory approaches, potential contents were analysed and a first draft was written. Through several feedback rounds, this draft was refined to the definition that is presented here. Professional nursing is defined in two core sentences. As regards content, it relates to promoting and maintaining health, preventing health problems, and assisting people in treating illnesses and in dealing with consequences of illnesses and their therapies. The goal is to achieve the best possible results of treatments and care as well as the best possible quality of life in all phases of life until death for the people cared for. Eight additional paragraphs describe to whom professional nursing is directed, the tasks it includes, its essential basics, who delivers it, how it is put into practice, and its context. The definition has a scientific background and incorporates international perspectives and developments. An addendum outlines further thoughts regarding interprofessional collaboration in health care, focal points of nursing education, and future directions of professional nursing. It calls for an optimal collaboration among the different professional groups to reach the best possible outcomes for people with (potential) health problems. Trends in society and health care, especially the growing numbers of old and chronically ill people, will increase the need for professional care. It is necessary to develop new systems and models of care that meet population needs and have a lasting effect. Nursing education must take these future changes into consideration.