  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.
