Message from the Program Chairs We are delighted to welcome you to the 27th edition of the International Conference on Real-Time Networks and Systems (RTNS), in Toulouse, France. RTNS is a friendly conference with a great sense of community that offers excellent opportunities for collaboration as well as a high-quality technical program. RTNS publishes papers addressing temporal issues in any area of computation and communication, at any level of abstraction, and in any application domain.This year we received 37 submissions and accepted 20 papers. The reviewing process involved 44 program committee members, who were assisted by 22 additional reviewers. Each submission received at least three reviews. Among the accepted papers, 4 outstanding papers were chosen, which are highlighted in the program, from which a separate committee selected one best paper and one best student paper. The conference program features a keynote talk giving a view on future challenges for the real-time community by Prof. Marko Bertogna (University of Modena, Italy), an industrial session on real-time challenges in four selected industrial application domains: automotive engine control systems (by Continental AG); automatic air transport (by Thales AVS France); electric smart grid substation automation systems (by SCLE-SFE, Groupe ENGIE); deterministic networking (by Cisco), and 6 technical sessions for accepted papers: analysis and validation; fault-tolerance, security, and data-flow; networking I and II; processor scheduling; and synchronization, preemption, and coordination. The main conference is also again complemented by the Junior Researcher Workshop on Real-Time Computing (JRWRTC), which is now in its 13th successful year.We would like to thank our many colleagues who have contributed to the success of RTNS 2019. First of all, we thank the Steering Committee for trusting us to manage the technical aspects of the conference. We also owe sincere thanks to all the PC members and reviewers who completed the crucial reviewing and shepherding work for the conference. The conference simply would not have been possible without the significant and sustained efforts of our General Chair, Jérôme Ermont (IRIT, ENSEEIHT, France), and the 5 members of the Local Organization Committee, who coordinated all aspects of the conference venue, web site, and the event itself. We also are grateful to the JRWRTC co-Chairs Antonio Paolillo (ULB, Belgium) and Benjamin Rouxel (UVA, Netherlands), and to the 15 members of the Workshop Committee for their efforts. Last but not least, we would like to thank the authors of all submitted papers – by entering your work into the process of review, critique, and possible rejection, even papers that were not accepted have helped to drive the important process of advancement in our field. We know it can be frustrating to have a paper rejected, but we hope that for each paper the reviewing feedback was helpful. Finally, we would like to thank the participants attending RTNS 2019 in Toulouse. We hope you will enjoy the technical program, the social events, and the conference venue and its surroundings! Ye-Qiong Song (LORIA - Université de Lorraine, France)Christopher Gill (Washington University in St. Louis, USA)RTNS 2019 Program Committee co-Chairs.