Solidarity, traditionally understood as the foundation of social cohesion, is caught in-between opportunities and challenges of digital technologies. The article first examines theoretical foundations, in particular classical, religious and contemporary approaches to solidarity, and shows how its concept is being transformed by technological influences. Second, the role of solidarity in digital spaces is analyzed. Here it becomes clear how digital technologies not only create new forms of networking, but also challenge existing moral and social values, even those with ties to the religious sphere. The third section focuses on the political dimension: The digital structural transformation of the public sphere is changing the conditions under which solidarity, understood as a fundamental principle of Christian social ethics, can act as a political principle. The article concludes with the proposition that solidarity must be rethought in the context of digitalization in order to stay meaningful as a moral and political guiding principle.