Internet-based information and communication technology (ICT) have increasingly been used to facilitate and support democratic engagement in society. A growing body of research has demonstrated that the Internet and, in particular, social media have given citizens the opportunity to participate, interact, network, collaborate, and mobilize themselves within communities. While these media have broadened the means of exercising citizenship in many forms of participatory democracy, the technological prerequisites exist to go beyond the standard uses of social media (e.g., social networking, entertainment) and towards proactive and co-creative democratic engagement. Such engagement includes, but is not limited to, participatory activities for democratic purposes. Further, some researchers have argued that representative democracy is in decline and has several limitations related to citizens’ trust in politicians and engagement with representative institutions. There is a recognition among scholars to infuse representative democracy with participatory bottom-up processes by employing ICT in an attempt to bridge these limitations. In order to further facilitate and support participatory as well as co-creative processes, this thesis elaborates a concept of co-creative media. The process of this work was guided by the following question: How can co-creative media be theoretically anchored and conceptualized in order to facilitate and support citizen engagement within democratic processes? A concept-driven design research approach was adopted to address this research question, and this resulted in five interconnected articles. Firstly, based on the results from each article, four design guidelines were formulated to further guide the design of co-creative media for democratic engagement. These design guidelines may support future participatory design processes in which stakeholders collectively contribute to the development and evaluation of co-creative media. The guidelines constitute a resource that stakeholders may use to develop adaptations of co-creative media for the purposes of facilitating democratic engagement. Secondly, the results from each article were fed forward into the concept-driven research process as theoretical and empirical insights, which were used to inform and elaborate the main contribution of this thesis, namely the concept of co-creative media. The concept of co-creative media in its form outlined by this thesis seeks to broaden citizens’ democratic engagement by means of creating virtual spaces in which new ideas, initiatives, knowledge, solutions, and digital tools could emerge. The implications of co-creative media could be to create, develop, and strengthen partnerships between communities and local services, extend digital skills in society through community-engaged practitioners, and propagate as well as coordinate large-scale co-creative practices.