Proceedings of the Sixth International Conference on Applied Category Theory 2023

The Sixth International Conference on Applied Category Theory took place at the University of Maryland, 31 July -- 4 August 2023. This conference follows the previous meetings at Leiden (2018), Oxford (2019), MIT (2020, fully online), Cambridge (2021) and Glasgow (2022). The conference comprised contributed talks, a poster session, an industry showcase session, and a session where junior researchers who had attended the Adjoint School presented the results of their research at the school. Information regarding the conference may be found at (https://act2023.github.io/). The contributions to ACT2023 ranged from pure to applied and included contributions in a wide range of disciplines in science and engineering. Submission to ACT 2023 had three tracks: extended abstracts, software demonstrations, and proceedings. Only papers submitted to the proceedings track were considered for publication in this volume.