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.