This book constitutes the proceedings of the 29th IFIP WG 1.5 International Workshop on Cellular Automata and Discrete Complex Systems, AUTOMATA 2023, which took place in Trieste, Italy, in August/September 2023. For AUTOMATA 2023, 7 full papers have been carefully reviewed and selected from 11 submissions. The book also contains 3 full papers from AUTOMATA 2022, which have been selected from a total of 18 submissions. In addition, the proceedings contain one invited talk in full paper length from AUTOMATA 2023.