In this special issue of IEEE Transactions on Visualization and Computer Graphics (TVCG), we are pleased to present the journal papers from the 23rd IEEE International Symposium on Mixed and Augmented Reality (ISMAR 2024), which will be held as a hybrid conference between October 21 and 25, 2024 in the Greater Seattle Area, USA. ISMAR continues the over twenty-year long tradition of IWAR, ISMR, and ISAR, and is the premier conference for Mixed and Augmented Reality in the world.