This volume constitutes the proceedings of 35th International Symposium on Logic-Based Program Synthesis and Transformation, LOPSTR 2025, held in Rende, Italy, during September 9–10, 2025.The 17 full papers and 4 short paper included in this book were carefully reviewed and selected from  21 submissions. These papers cover all aspects of logic-based program development, all stages of the software life cycle, and issues of both programming-in-the-small and programming-in-the-large.