The proceedings include papers presented at the 10th International Symposium on Tunnel Safety and Security (ISTSS) held in Stavanger on 26-28 April 2023. The symposium is well established in the tunnel fire community and the success of ISTSS is a tribute to the pressing need for continued international research and dialogue on these issues. The proceedings provide state-of-the-art knowledge in the field of fire safety and security in tunnels and other underground structures. We clearly see that the fire and explosion hazards of alternative fuel vehicles have become a major area of concern. The airport car park fire in Stavanger 2020 involving alternative fuel vehicles is an example of the challenges ahead. Inside an underground construction such incidents would be more severe. The research on alternative fuel vehicle safety is in urgent need and it is becoming one of the most important research fields. Furthermore, tunnel digitization emerges as a new research area, while risk and engineering analysis continues to be a focused area of many papers. This year there are also specific focuses on fixed fire fighting systems and evacuation.