The 26th European Conference on Artificial Intelligence (ECAI 2023) took place from 30 September – 4 October in Krakow, Poland. On the final day of the conference, the outstanding paper awards were announced. There were two winners in the ECAI 2023 Outstanding Paper category, and one winner in the Outstanding Paper for AI in Social Good category. Abstract: Learning effective strategies in sparse reward tasks is one of the fundamental challenges in reinforcement learning. This becomes extremely difficult in multi-agent environments, as the concurrent learning of multiple agents induces the non-stationarity problem and sharply increased joint state space.