This volume comprises selected papers from the SIAM International Meshing Roundtable Workshop 2023, SIAM IMR 2023, held in Amsterdam, the Netherlands, March 6-9, 2023. The IMR was started by Sandia National Laboratories in 1992 and, since 2021, it has been held under the umbrella of the Society for Industrial and Applied Mathematics (SIAM). The SIAM IMR 2023 was the first in-situ conference to be held since 2019, after two online conferences. It consisted of short courses, technical presentations from keynotes, contributed talks and research notes, a poster session and meshing contest, and discussion panels. The papers in these proceedings present novel contributions that range from theoretical advances to technical applications in engineering, geometric modeling, computer graphics, visualization, and machine learning.