This special issue includes extended and substantially revised versions of selected papers presented at the MathAI 2026 Conference on Mathematics and Artificial Intelligence. Submissions to this issue were open to conference participants and were selected based on their relevance and scientific quality. All submissions included in this issue have undergone peer review as part of the conference evaluation process (e.g., via the OpenReview platform) and were subsequently subject to additional editorial assessment by the journal’s editorial board to ensure their originality, scientific contribution, and suitability for journal publication. Authors were required to submit extended versions of their conference papers with significant new content. This issue covers research in the mathematical foundations of artificial intelligence, optimization, statistical learning, neural network theory, and computational methods. Publication model: Special issue based on conference-reviewed and extended submissions (MathAI 2026).