The CCIS book constitutes selected papers of the 12th International Conference on Computational Science and Computational Intelligence, CSCI 2025, which took place in Las Vegas, NV, USA, during December 3–5, 2025.For this book, 24 papers from the Research Track on Artificial Intelligence, CSCI-RTAI, are included from 389 submissions. In addition, 9 papers out of 36 submissions from the Research Track on Computational Intelligence, CSCE-RTCI, are included, and 8 papers were selected from 78 submissions to the Research Track on Social Network Analysis, Social Media and Mining, CSCI-RTNA. The papers were organized in topical sections as follows: Artificial Intelligence - Deep Learning Methods, Industrial Applications, and Algorithms; Artificial Intelligence - Algorithms and Application; Computational Intelligence; and Social Network Analysis, Social Media and Mining.